• Preheat oven to 400 degrees F. Remove the pie crust from the refrigerator and let it rest at room temperature while you prepare the bacon and onions.
• Cook the bacon in a saute pan over MEDIUM-HIGH heat, stirring frequently, until crisp. Use a slotted spoon to transfer the bacon to a double layer of paper towels to drain. Leave the bacon drippings in the skillet.

Caramelize the Onions

• Reduce heat to MEDIUM and melt the butter with the bacon drippings in the skillet. Add the onions and ¼ teaspoon salt and cook, stirring frequently, for 5 minutes. Cover and cook for about 8 to 10 minutes, stirring every 2 minutes or so and then covering again, until the onions are soft and golden brown. If they begin to burn, reduce the heat under the skillet, as needed. Uncover and cook for an additional 2 to 3 minutes or until deep golden brown and any liquid in the skillet has evaporated. Remove the skillet from the heat and allow the onions to cool while you parkbake the crust.

Parbake the Crust

• Coat the bottom and sides of a nonstick 9-inch tart pan with a removable bottom with nonstick cooking spray.
• Set the pie crust down, centering it in the prepared tart pan. Press it down across the bottom and up the sides of the pan, pressing it into the grooves of the tart pan. If there is a slight overhang of crust around the top edge of the pan, fold it over (towards the inside of the pan) and then press it flat against the sides. The top of the crust should be flush with the top of the tart pan. Lightly prick the bottom of the crust all over with a fork.
• Line the pie pastry with a large sheet of regular (not heavy duty) aluminum foil. Press the foil down across the bottom and against the edges of the crust, pressing it into the fluted edges of the dough. Fill it with pie weights or dry beans, being sure there is weight against the edges of the crust.
• Place the tart pan on a baking sheet (for easy transport in and out of the oven) and bake for 14 to 16 minutes, or until dry (you can lift the foil and peek at the bottom of the crust). Remove from the oven. Carefully lift the foil and weights out of the crust and set the crust aside.

Prepare the Filling

• In a medium bowl, whisk the eggs with the sour cream (or crème fraiche) until smooth. Add the sage, thyme, remaining 1 teaspoon salt, pepper, and nutmeg and whisk again until well combined. Stir in the bacon and cooled onions. Pour the mixture in the prepared crust.

Bake the Onion Tart

• Bake at 400 degrees F for 25 to 30 minutes or until set in the center and golden brown. Remove from the oven and cool on a wire rack for 10 to 15 minutes. Remove from the tart pan, slice, and serve.
• Delicious served warm or at room temperature.