I loved this topping. 
Baked Halibut with Sour Cream, Parmesan and Dill Topping
Kalyn's Kitchen

2 pieces halibut, thawed if frozen and patted dry with paper towels
salt and fresh ground black pepper to taste
3 T sour cream
1/4 tsp garlic powder
1/4 tsp dill weed, dried
2 T finely ground Parmesan cheese
3 T sliced green onion (about 3 green onions)

Thaw frozen halibut overnight in refrigerator, then place in baking dish and blot dry with paper towels.  Let the halibut come to room temperature while you prep other ingredients.  Preheat oven to 375 degrees.  Slice 3 T green onions, then measure 2 T and finely chop them.  Reserve the other 1 T sliced onions to garnish the cooked dish (I put all three tablespoons in the sauce and omitted the garnish).  In a small bowl, stir together the sour cream,  garlic powder,  and dill weed.  Stir in the finely grated Parmesan cheese and green onions.  When fish has come to room temperature, use a rubber scraper to spread an even coating of this topping over each piece of the fish, using all the topping mixture.  Bake fish until the internal temperature reaches 145 degrees or until fish pieces feel firm but not hard to the touch.  (Use a fork to press down to test.)  Serve hot.