In a skillet sauté finely chopped onion in butter until soft; remove from the heat and set aside.
In a bowl combine eggs, yogurt, half-and-half, salt, pepper, cayenne pepper and the cooked onion; stir.
Crumble the cooked bacon and sprinkle in the 9-inch unbaked pie shell along with shredded Swiss cheese. Pour the egg mixture on top.
Bake at 350° F for 35 to 40 minutes, or until the top browns lightly and the center is set.Servings: 6