Preheat oven to 350F. Arrange fish in a shallow baking dish, salt and pepper liberally; cover with sliced onion; dot with butter. Bake 20 minutes or until fish flakes easily. Mix mayonnaise, mustard, lemon juice and hot sauce. Pour over fish and broil 2 to 3 minutes, until brown and bubbly. Sprinkle parsley over top of finished dish. Serve hot with lemon wedges.
Cajun Country -- New Iberia, Louisiana