From here: https://www.allrecipes.com/recipe/260110/creamy-halibut-olympia/

½ cup sour cream
½ cup mayonnaise
2 cloves garlic, diced
1 ½ teaspoons seafood seasoning (such as Old Bay®)
¼ teaspoon ground white pepper, or to taste
¼ teaspoon paprika, or to taste
1 sprig fresh dill, chopped, or more to taste
2 bunches green onions, chopped
¼ cup panko bread crumbs, or to taste
2 tablespoons drained capers, or to taste

Combine sour cream, mayonnaise, garlic, seafood seasoning, white pepper, paprika, and dill in a bowl. Season with salt. Pour on top of halibut. Sprinkle green onions, panko, and capers on top.

Bake in the preheated oven until the fish flakes easily with a fork, about 15 minutes.