In a 10- to 12-inch skillet over MEDIUM heat, cook the ground beef, onions, and bell pepper until meat crumbles and no pink remains. Drain off as much grease from the pan as possible and return the skillet to the heat.
Add tomato sauce, ketchup, Worcestershire, mustard, brown sugar, cumin, garlic powder, smoked paprika, crushed red pepper, and fresh ground black pepper. Stir well to combine and reduce heat to low. Simmer 10 minutes, stirring occasionally.
Meanwhile, preheat oven to 350 degrees F. Separate the slider buns and slice in half. Place bottom half of buns in a 13- x 9-inch baking dish.
Spoon some of the Sloppy Joe mixture on to each bun and then sprinkle each one with shredded cheese. Place top half of the bun over the cheese. Brush the tops of the buns with melted butter and sprinkle with sesame seeds.
Bake for 10 minutes, or until buns are lightly toasted and cheese has melted.