Preheat oven to 375 degrees. Defrost spinach and drain well.
Saute onion in butter until tender.
Beat eggs together. Stir in spinach, and mix together. Stir in feta cheese, cottage cheese, sauteed onions, and black pepper to taste.
Clean peppers: remove stems and seeds. Cut peppers in half lengthwise.
Fill peppers with spinach mixture and place in a buttered casserole pan. Sprinkle tops of peppers with Parmesan cheese. Bake for 30 minutes.
