1/4 cup butter
1 medium onion, chopped
4 pieces halibut fillets (or thawed frozen)
1 1/2 cups sour cream
1 1/2 cups mayonnaise
1 cup crackers, crushed (I use Ritz)
Preheat oven to 375 degrees.
Melt butter; pour into the bottom of a 13 X 9-inch baking pan.
Spread onion over melted butter and top with halibut fillets.
Mix together sour cream and mayonnaise; spread over halibut.
Top with cracker crumbs.
Bake in the oven until fish flakes and crumbs are lightly browned (about 20 minutes.)