In a large skillet melt butter. Then add olive oil. Add in the sliced onions.

Cook stirring occasionally for 15 minutes on low until soft then cook for another 45 minutes. If browning too much occasionally add 1/2 cup water if needed.Once done put on paper towels and cover as well. This will help with removing some moisture. (See notes for a quicker method)

Preheat oven to 400°

If using store bought dough remove from fridge and let it sit at room temperature for 10 minutes. Roll out onto greased pie dish. Prick crust with the fork on bottom and sides to prevent puffing. Bake for 10 minutes until golden brown. Cool completely before adding filling. Reduce temperature to 375°.

While baking crust, in another large skillet cook bacon over medium heat until most of the fat is rendered but not too crisp. Remove from pan and set aside to cool.

In a large mixing bowl beat together the eggs. Add the remaining 6 ingredients to bowl. Stir to combine.

Cut bacon into bite size pieces then add to bowl, followed by the onions. Stir to fully incorporate.

Pour into pie crust.

Bake for 35-45 minutes or until it is only slightly jiggly. Remove from oven and allow it to sit for 15 minutes to allow custard to set.