For the Sauce:

In a medium frying pan, saute onions in butter until softened. Add tomato sauce and Italian seasoning. Simmer for 10 minutes. Set aside 1 cup of the sauce and pour the remainder into a large casserole dish.

For the Pasta Shells:

Preheat oven to 350 F. Cook pasta shells according to package directions. Drain and rinse with cold water. In a large bowl, combine cottage cheese, mozzarella, egg, tuna or crab, green onions and pepper. Spoon a tbsp of the filling into each shell and arrange in single layer in casserole dish. Sprinkle with parmesan.

Cover and bake for 30 minutes. Serve with reserved sauce