0 1cof sour cream 1cof mayo 1medium onion, sliced 2pds of Halibut w/o skin 1to 2 cups of cheddar cheese 1cof sour cream 1cof mayo 1medium onion, sliced 2pds of Halibut w/o skin 1to 2 cups of cheddar cheese Place sliced onions on the bottom of casserole dish. Slice halibut into strips and place on top of onions. Mix Mayo and Sour Cream together. Spread over Halibut. Top with Cheese. Bake at 350 for 30 to 35 minutes. No need to cover.