My new favorie recipe:

2 lb halibut fillet
1 cup sour cream
1 cup mayonnaise
1/4 cup chopped green onions
3 tablespoons freshly squeezed lemon juice
2 cups crushed Ritz crackers
1 large yellow onion, sliced
1/4 cup butter

Melt butter in a large frying pan. Add sliced onion and sauté until onion is translucent then spread evenly over bottom of baking pan; set aside.
In a bowl mix together sour cream, mayonnaise, green onions and lemon juice. Arrange halibut over top of a bad of onions in baking pan. Spread sour cream and mayonnaise mixture over the top of the halibut. Sprinkle generously with crushed Ritz crackers.

Bake at 375°F for 40-50 minutes (depending on thickness of fish).