Here's a great recipe for baked salmon(wild Alaskan salmon of course), but I bet it would be great on halibut or really any type of fish. This is courtesy of my mother-in-law...she's the one who gave me the recipe.
I typically use 1-2 medium sized fillets with skin still on.
1/2-1 onion thinly sliced
Equal parts of sour cream and mayonnaise(it will depend on how much you need to cover your fillets)
A little bit of lemon juice...like a tsp or 2
A little bit of apple cider vinegar...again like a tsp or 2
Mustard- 1 tsp
salt, pepper, garlic powder/granules, onion powder to taste
Lay fillet skin side down in pan. Salt and pepper fillets. Lay slices of onion on fillets. Pour mixture over the fillets. Bake for 30 minutes at 400*.