Preheat oven 425°. Press pie dough into pie plate. Cover with foil but press the foil down so it's touching the pie crust all the way around and up the sides. Fill the foil with pie weights (if you have them). I use rice, dry beans work great too. This helps the crust to avoid puffing up when pre-baking it. Bake for 10 minutes. Remove weights and foil, bake for another 2-3 minutes. Gently press air out if it puffs up, set aside.

While the pie crust is pre-baking, place bacon and onions in a large skillet over medium heat stirring occasionally. Once the bacon is close to being crisp, stir in chopped spinach. Season with a bit of black pepper. Cook until spinach is wilted and bacon is crispy. Remove with a slotted spoon onto a paper towel lined plate to drain.

In a medium bowl whisk together eggs, heavy cream, salt, pepper, and cayenne pepper.

Evenly arrange bacon mixture onto the bottom of the pre-baked pie crust. Sprinkle with Swiss cheese. Pour the egg mixture over the top and tap the pie plate on the counter to remove any air bubbles and allow the custard to fill-in through the bacon filling. Bake at 425° for 10-12 minutes. Reduce oven temperature to 325° and bake for another 30 minutes, or until set in the center. If the pie crust edges start to get too brown, cover just the crust edges with a bit of foil to prevent burning.

Rest for 5 minutes before slicing. Can be served ward or room temp.