Tomato-Topped Fish Fillets
["1 1/2 Tbsp. butter or margarine", "2 Tbsp. lemon juice", "1 (16 oz.) pkg. frozen cod, ocean perch or flounder fillets, thawed", "onion salt", "1/2 tsp. salt", "1/4 tsp. pepper", "1 medium tomato, sliced"]
["About 30 minutes before serving:", "Preheat oven to 350\u00b0.", "In a large, shallow baking dish in oven, melt butter or margarine. With pot holders, remove dish from oven; stir in lemon juice.", "Dip fillets in mixture, turning to coat both sides."]
["butter", "lemon juice", "frozen cod", "onion salt", "salt", "pepper", "tomato"]