In a food processor, pulse flour and salt to mix.
Add butter and pulse several times to mix the dry ingredients with the butter.
Add ice cold water and apple cider vinegar.
Pulse the food processor to create a sandy like mixture.
remove the dough from the food processor and shape into a square.
Cover the dough in plastic wrap and refrigerate for 30 minutes.
Remove the cold dough from the refrigerator and roll out to a 12-14 inch circle on a floured surface.
Gently lay the dough into a 9 inch pie plate. Poke holes in the bottom of the dough with a fork and shape the outer crust.
Place the pie plate in the freezer while mixing the filling.
Preheat the oven to 425℉.
In a large mixing bowl, combine eggs, heavy cream, salt, sugar, cayenne, and black pepper.
Once the oven is preheated, remove the pie plate from the freezer.
Sprinkle the cooked chopped bacon, minced onions, and gruyere cheese over the dough.
Pour the egg mixture into the pie plate.
Bake at 425℉ for 15 minutes.
Reduce the temperature of the oven to 300℉ and continue to bake for 30 minutes. Internal temperature should be 175℉.
Allow the quiche to cool for 10 minutes before cutting.
Can be served immediately. Leftover quiche can be refrigerated, covered, for 5 days