A homemade Cajun spice mix adds incredible flavor to this Blackened Mahi Mahi. It’s a quick dish you can easily pull together on a busy weeknight but it’s so tasty you’ll want to serve it to guests!
This is a new recipe for me and it came about after Paul and I had a meal at a nearby restaurant. We both ordered the mahi mahi special that was served with mashed sweet potatoes and veggies, and then we basically freaked out about how good it was for at least two days after and it haunted us in our dreams…. we’re weird.
This all had me wondering why the heck I never make mahi mahi at home. So, of course, I had to make some mahi mahi.
I set out to capture the same flavors we had in the restaurant dish and knew I definitely had to pair it with sweet potatoes, just like they did. The sweetness perfectly complements the slightly spicy fish in a soul-satisfying way. It’s truly a perfect flavor combination and it also happens to be SO good for us.
Say hello to my new favorite item from Costco. This great big package of Wild Caught Mahi Mahi contains skinless, individually vacuum-packed portions of incredibly fresh mahi mahi. I pop this bag in my freezer and pull just the number I need. The fish is FRESH, people. There is zero fishy aroma in the house after cooking it.
Mahi Mahi is a mild, firm textured white fish that is wonderfully tender – almost buttery – when prepared properly. It’s a fabulous source of lean protein and packed with nutrition. If you’ve got young ones who are squeamish about seafood, this would be a great one to try on them. Yes, blackened fish can be quite spicy. but when you make your own spice mix you get to decide precisely how spicy you’d like it. I’ll show you how!
To make the Kickin’ Cajun Seasoning Mix, grab a small bowl and combine 1-1/2 teaspoons onion powder – 1 teaspoon each of smoked paprika, oregano, granulated garlic or garlic powder, thyme, and salt – and 1/2 teaspoon each of black pepper and cayenne pepper. The only spicy item here is the cayenne so feel free to adjust the amount to suit your taste. At 1/2 teaspoon, the fish will be mild to moderate on the spice scale. I’m a bit of a wimp and it is perfect for me. If I had little ones, I’d reduce it to 1/4 teaspoon or even eliminate it all together. My big boys would tell me to add more!
Update – By popular demand I’ve published a recipe for a big batch of the Kickin’ Cajun Seasoning Mix. Check out the post for other delicious ways you can use this flavor-packed blend.
If you are using frozen mahi mahi, be sure to allow it to thaw completely (24 hours) in the refrigerator. Pat the fillets dry with paper towels so the spice mix will adhere nicely.
Sprinkle both sides of the fillets with the spice mix and use your clean hands to pat the mixture into the flesh of the fish. Then, of course, wash those hands again.
Melt 2 tablespoons butter and 1 tablespoon olive oil in a large skillet over medium-high heat. Get the pan as hot as it can get, without burning the butter, and then add the seasoned mahi mahi. You want that nice sizzle when the fish hits the pan. Cook it a good 3 or 4 minutes on one side until nicely golden brown, then flip it and let it go a few minutes on the other side. You don’t want to overcook it so be vigilant and pull the pan off the heat just as soon as it’s cooked through and flakes easily with a fork.
Remove the fish to a serving platter and squeeze fresh lemon juice over the top. A little citrus is a necessary thing when cooking fish as far as I’m concerned.
Oh, and before I go, if you’d like to serve this with mashed sweet potatoes, here’s how I did it. Place a couple of red-skinned sweet potatoes in a large pot and cover with water. Bring to a boil, reduce the heat and bring the water to a nice simmer and cover the pot. Cook the potatoes for 45 minutes to an hour, or until they pierce easily through with a knife. Remove from the pot to cool for just a couple of minutes. Use paper towels to pull the skin off and then mash the potatoes with a touch of light sour cream and salt. Perfect every time.
Blackened Mahi Mahi
Blackened Mahi Mahi
You can easily control the level of spiciness in blackened fish by making your own Cajun spice mix. This is a super fast, incredibly delicious way to add more seafood to your diet.
Ingredients
- 4 mahi mahi fillets, approximately 6 ounces each
- 2 tablespoons butter
- 1 tablespoon olive oil
- 1 lemon
Kickin’ Cajun Seasoning Mix:
- 1 1/2 teaspoons onion powder
- 1 teaspoon garlic powder
- 1 teaspoon smoked paprika
- 1 teaspoon dried thyme leaves
- 1 teaspoon dried oregano leaves
- 1 teaspoon salt
- 1/2 teaspoon freshly ground black pepper
- 1/2 teaspoon cayenne pepper, or to taste
Instructions
Combine all Kickin' Cajun Seasoning Mix ingredients in a small bowl.
Pat fillets dry with paper towels. Season the fillets liberally with Kickin' Cajun Spice Mix on both sides, pressing the seasoning into the fish with your hands. Wash hands thoroughly.
- Place a large saute pan over medium-high heat and add butter and oil. When the fat is nice and hot, add the seasoned fish. Cook, undisturbed, for several minutes, until golden brown on one side. Flip fish over and continue to cook until opaque and completely cooked through.
- Squeeze lemon juice over the fish and serve.
Recipe Notes
If you're cooking more than 4 fillets or would like to add a more generous amount of seasoning, follow my recipe to prepare a big batch of Kickin' Cajun Seasoning Mix.
Nutrition
Amy @ The Blond Cook says
This is making me dream of summer, Valerie! Every year I love going fishing for mahi and it is one of my favorite foods. Yours looks amazingly delicious!
Cathy K says
This was really good! I had just taken a couple of the Kirkland Mahi fillets out of the freezer and decided to look for a recipe! I upped the cayenne, but next time I’ll stick with your recommendation. It was just a little too spicy for me, but I’m a wimp!!
Valerie says
Hi Cathy. I’m with you on the wimp thing! A little cayenne goes a long way so I always try to hold myself back from using too much. It really is a very tasty seasoning mix and can be used on all sorts of things. I’m so glad you enjoyed it! Aren’t those frozen fillets from Costco the best? Thanks for the lovely comment 🙂
Deborah Ann says
This was absolutely amazing!! Used th Kirkland Mahi also, used 3 for the recipe, was barely enough rub though, I think this recipe is really for two but I put it on thick. We both love it. Followed the recipe exactly. Cooked in a cast iron skillet, 4 min per side. Whipped sweet potatoes were a great add with coleslaw. Thank you!
Valerie says
Hi Deborah! So glad it worked out for you. Made as directed it does make a very light coating of the rub. I often times will double it if I really feel like laying it on thick so thank you for mentioning this. This was on our menu this week too!
Lynn says
Hi Valerie, I love this recipe and I cook in my oven at 425 degrees, in a very hot iron skillet. I place a tablespoon and one-half of a tablespoon of oil (I use canola as olive oil smokes at that temp) into my iron skillet. I placed in the pre-heated oven while I prepare my Mahi-Mahi. I have been purchasing this fish from COSTCO for a few years now is,,,, it is wild caught in U.S. waters. Once I have my fish coated, I take the skillet out and put the fish into the hot skillet….it just sizzles! I put it back in the oven for approx. 6 minutes, take out and flip the Mahi Mahi over and sprinkle a little more of the rub (or if in a hurry, I used Old Bay Blackening Seasoning…no other) and put back in the oven and cook another 5-6 minutes or until it is a little crispy around the edges, though not too much. It is one of my husband’s favorite dinners.
Valerie says
It sounds wonderful, Lynn. Aren’t those filets from Costco just the best? I’ve been preparing both the mahi mahi and salmon about once a week since I’ve discovered them. So fresh and honestly the best tasting fish I’ve found anywhere. Thanks for all your great tips!
Jodi says
This was AWESOME! I’m not a huge fan of spice but I do like a little more these days than I used to. I made it exactly as you have written, It was excellent but a tad bit too spicy to my liking so I will reduce the cayenne to 1/4 teaspoon next time and I’m pretty sure it will be perfect for what we like 🙂 Thanks for sharing my husband and my son both really liked the flavor of this recipe!
Valerie says
That’s great, Jodi! We really love this dish as well and it has become a regular on our menu. Thanks so much for your wonderful comment 🙂
KBlack says
Have you ever tried this rub on other fish….I’m thinking salmon. I wonder how it would turn out??? I tried this recipe as written before and it’s EXCELLENT! Hubby and I loved it and it pairs perfectly with a sweet potato. I’ve also paired it with “garlic butter roasted carrots” from pintrest as well and those were to die for.
Valerie says
I haven’t tried it but I just know it would be fabulous on salmon! Those carrots sound yummy. It is really nice to pair blackened fish with a side that has a bit of sweetness to it – like sweet potatoes or carrots. Great choice! So glad you and your hubby are loving it 🙂
Alissa says
I used your blackened seasoning recipe. DELICIOUS! I cooked my fresh mahi mahi sous vide first with minced garlic, then seared it with your blackened seasoning and it was the best mahi mahi I’ve ever had. Thanks for the recipe!
Valerie says
Hi Alissa. That sounds incredible! I’m sure the sous vide made it butter soft. So glad you enjoyed the seasoning mix!
Karin says
This recipe is awesome, transforms ordinary into extrordinary. I use that same cajun spice mixture wand added 2 tbsp of panko for chicken stuffed with spinach and pepper jack cheese. Such an amazing spice mixture, thanks for posting.
Valerie says
You got it, Karin!
Nancy O'Connell says
I love the spice mix! I’m going to mix up a batch and store it in a jar for an even faster dinner. Thank you!
Terence says
Made this tonight using fresh mahi mahi filets. Worked great. Great spice rub and a very quick and easy dinner.
Lizette says
Yummy recipe! Next time I will add more cayenne…needs more heat. I also tried the oven/cast iron skillet method of cooking. Super easy! Tomorrow I’m off to Costco to pick up the frozen Mahi Mahi everyone has raved about. Thanks Valerie.
Valerie says
Glad you enjoyed it, Lizette! I just picked up two packages of the Mahi Mahi from Costco last week and I’m looking forward to making this very soon 🙂
Nicki says
Very quick and tasty. I reduced the cayenne to 1/4 t and increased the oregano and thyme. It was delicious.
Jody says
Got two lovely fillets of mahi mahi this morning. I’ve only made tacos with it before, so I went to the net for ideas. This is perfect, since I coincidentally, also bought sweet potatoes. Thanks for the idea. I will replicate it to the T!
Evelyn says
The recipe is just wonderful. Making it as written for the second time. A real family favorite.
Valerie says
Fantastic! So glad to hear this, Evelyn. 🙂
Kelly D says
Just made this after a quick search turned up your recipe. So glad I found it. The Costco Mahi Mahi is a special treat I buy for myself two or three times a year but after tasting this I think the frequency is going to skyrocket. Oddly enough I had taken the fish out yesterday so I “had” to cook it tonight lest the fish go off in the fridge. None of us were hungry after a late afternoon lunch so the plan was to reheat tomorrow. Well, there’s only one piece left. I made one disappear and then my wife and two young daughters snacked away the other two. It was irresistible! Definitely going to make a big jar of the spice mix for quick Cajun taste on fish, chicken and probably pork too!
Valerie says
Yay, Kelly! So glad to hear you loved it. I’m endlessly impressed with the quality of Kirkland brand frozen fish. The salmon is wonderful too. Thanks so much for your comment. 🙂
Kelly D says
Just a follow up for you. Tried it with pork tonight – same cooking method. Yum-yummy!
Nancy Peloquin says
So easy & delicious! Husband loved it! Replaced cayenne with chili powder.
Yolanda Ayala says
Easy and delicious, my family enjoyed it. My twelve who is not a fan of fish gave this recipe a thumbs up! Thanks for sharing..
Art says
Blackened mahi-mahi is such a treat that even my finicky teen-age daughter loved it. So simple to prepare, delicious and nutritious. Costco ought to print your recipe right on the label. Added turmeric with excellent results and plan to add fenugreek to next batch. Guru insists it’s the miracle cure!
Since sweet potato takes such a long time to boil I cooked extra and kept them in fridge for several days. Easy to peel and mash cold, then heated for one minute on frying pan as soon as fish was removed. Used a pinch of cumin instead of sour cream.
Brettani Shannon says
fantastic recipe! Super easy and fast and a whole family loved it! I did a whole family loved it! I did take it easy on the Cayenne for the kiddos and it was still great! Thank you for the awesome recipe.
Sean says
Hi Valeri,
I just got stationed in Okinawa Japan & the FRESH seafood that is available is just sick!
I’m a tru Kountry Boy for TN, Smoked everything that makes a sound. Except fish, 😉
So I decided to venture out & attempt my hand at seafood, since that is the dominant cuisine & came across, well you & your Mahi Mahi recipe. I will try it this weekend & post the results, good or bad.
One question though, your sweet potato recipe states to use “peeled” potatoes prior to boiling. Then it states after boiling to remove the skins. do I boil with or without skins? Thanks.
Valerie says
Hi Sean. There’s no need to peel sweet potatoes before boiling. They will practically fall right off once they are cooked. Hope you love the recipe!
Eda says
Absolutely outstanding! Best fish I have ever made OR tasted- and I’ve made and tasted just about everything. 🙂
Valerie says
Fantastic, Eda! So glad you enjoyed it. 🙂
Jon says
This recipe is fantastic! I tried it the other day after I caught a mahi-mahi on the boat down near Mexico. I know your recipe called for the Kirkland mahi, but I just couldn’t pass up on the freshly caught one.
Valerie, if you think your readers would like to learn how to sustainably catch the fish they are eating, I’d be humbled and honored if you’d include the guide I wrote about it in this post: https://castandspear.com/dorado-fish/. I feel it’s always important to know where your food comes from.
P.S. I can’t wait to try more of your recipes 🙂
Chuck says
When my wife and I spent a week on Oahu last summer, we ate fresh mahi every day. It’s a wonderful fish. The Hawaiians don’t use blackening to my knowledge just mild seasoning.
Julie says
Made this tonight using fresh Mahi Mahi – it was delicious!
Joann says
This recipe was just what I was searching for. My husband will soon have surgery and will be limited (not allowed) spicy foods for a couple months. He loves mahi mahi and I love spicy so its a compromise, but one I’m willing to take for his health benefit. I’ll leave the cayenne out (so sad) but I’ll make it for him and put the cayenne in again when he gets better. Thanks so much for this recipe.
michelle says
This was an awesome recipe! My husband is a picky eater & he ate everything. Thank you. Looking forward to checking out more of your recipes.
KP says
Great spice mix! I’m big on heat so tossed in a little more of the cayenne and added chili powder also. Needed some inspiration for the mahi sitting in my freezer and just so happened to already have been making mashed sweet potatoes. This was great, and I’ll definitely make it again. Thank you!
Sheneqa says
I had no idea how to cook mahi mahi so I decided to look up a recipe. This is now my favorite fish! It was delicious! My husband was shocked at my “skills” and agreed that it tasted like a dish from a gourmet restaurant! Thank for this simple and easy recipe. It’s now my “go to”!
Donna says
Made this for my husband – he loved it so much that I made it again two days later. (Mahi was on sale at local grocer in South Carolina.) I don’t go crazy for blackened anything but I may have to try it myself – without red pepper/chili powder (I did not have cayenne) because he was so thrilled. I made the sweet potatoes too – that was perfect and he thought he didn’t like sweet potatoes that much – now he loves them. Thank you.
Valerie says
My husband thought he hated sweet potatoes when I met him too and he was quickly convinced otherwise! I hope you are doing well there in South Carolina through all of this scary weather. Thanks so much for your comment, Donna. 🙂
Brian S says
The recipe sounds great – we’ll try it. We get the same Mahi Mahi from Costco. It’s wonderful. I usually grill it on my charcoal Weber.
Dave S, Palm Coast Florida says
I picked up some fresh mahi at a local fresh air market this morning. After looking over a few recipes, your’s was the one I was looking for. I wasn’t disappointed, even though I had to omit the cayenne to suit my wife’s bland preferences.
This was very good. The spice combination accented the mahi perfectly. Best of all, Elaine ate all of her fish and complemented the recipe, something she almost never does (eating all the fish, that is).
Except for the cayenne, and using some ghee instead of butter, I followed your recipe as written. I’ll serve it to guests next time.
PETER DENNIS says
Frozen fish is not “FRESH'”. I despair. But Mahi Mahi is lovely. Especially fresh!
Valerie says
Hi Peter. If you have access to fresh mahi mahi you can absolutely use this recipe and I’m sure it will be wonderful. The wild caught frozen mahi mahi from Costco is a high quality option that we love.
Heidi Harper says
WOW! This was delicious….just the right amount of heat. My 11 year old daughter even loved it! Served with cauliflower mashed potatoes and roasted Brussels sprouts! AMAZING!
Lissa says
Delicious! Just perfect. I, too, just came home with the big bag of Mahi Mahi from wonderful Costco and wasn’t sure which direction to go. Salmon has been our go-to for years and I wanted to switch it up. The spice seasoning is so great, dinner was amazing. I did one side on the med-high, flipped and lowered to medium to prevent butter burn and too much blackening. Thank you!
Valerie says
Fantastic! We love this seasoning on salmon too so you might want to give that a try if you are salmon fans.
Susan says
Great and so very easy. We were looking for recipes that have lots of flavor to keep the fish from being too bland. This was perfect. Thanks!
Jana says
I do not eat fish. Too fishy tasting. But this mahi recipe is a 5 star in my book. Thank you so much!
Valerie says
You’re very welcome, Jana. So glad you liked it!
Kelley L. Sharp says
Excellent recipe!! Easy-Peasy, fast & delicious!!
Cathy says
My husband and I loved this, except we’ll cut the salt way down next time. Thanks for a delicious new way to enjoy our mahi mahi!
Melodie K Garner says
Oh my! Where has this been?! Very tasty and soooooo easy!
Virginia says
Made this tonight for dinner with coconut jasmine rice and roasted broccoli. We all thought it was too salty, so next time I will half the salt. I also used 1/2 tsp of chipotle instead of cayenne. Winner in my house! This recipe is getting printed and put in my binder.