Ok here is the recipe word for word from my old cookbook
Bubbly Baked Fillets
1 lb block frozen fish fillets
1 can cream of mushroom soup
2 tbsp. finely chopped onions
1 tbsp lemon juice
1/2 cup shredded cheddar cheese
Thaw fillets just enough to allow cutting into 3 or 4 pieces. Place in shallow greased baking dish that just holds the fillets almost touching. Combine soup, onion, and lemon juice and spoon over fillets. Top with grated cheese. Bake at 450F just until the fish may be easily flaked with a fork and the sauce bubbles (about 25 minutes) yield 3-4 servings