Rub the bottom of a glass bake dish with a small amount of butter or margarine. Lay fillets in one layer in the dish. Squeeze 2 or 3 orange quarters over the fish, then sprinkle sesame seeds, garlic powder, onion powder and parsley over the top. Sprinkle a little Parmesan cheese over the top if desired. Bake in a hot oven, 425 degrees for 10 - 15 minutes, or until fish flakes easily with a fork.