Preheat the oven to 375 degrees F (190 degrees C).

Cook onions in a medium skillet in some butter until softened and translucent, stirring often, about 10 minutes. Reserve juices.

Combine onions, sour cream, and eggs in a large bowl. Stir in onion juices, 1/2 cup butter, and 1/4 cup Parmesan cheese; season with hot sauce, salt, and black pepper. Make sure all ingredients are well blended; divide between 2 pie shells. Sprinkle remaining 1/2 cup Parmesan cheese and paprika on top of pies.

Bake in the preheated oven for 20 minutes. Reduce oven temperature to 350 degrees F (175 degrees C); continue baking until lightly browned on top, 30 to 40 minutes more. Cool to settle before slicing, 3 to 5 minutes.