Place fish on an oven-proof platter or in a shallow baking dish.
Sprinkle with Tony's Creole Seasoning or salt and pepper to taste.
Arrange onion and lemon slices on top.
Mix ketchup, sherry and margarine; pour over fish.
Bake in a moderately hot oven (375°) for 50 minutes to 1 hour or until fish flakes when tested with a fork. (Serves 5 to 6)
Servings 0