Way too easy!
Just lightly oil a baking dish to fit the fish (cut into serving portions if you wish), place fish in & top with whatever suits your fancy. Sometimes I do a sort of "piperade" mixture of stewed tomatoes, onions, & cooked bell peppers; other times a sort of Greek treatment with diced or sliced tomatoes, sliced red onions, fresh chopped oregano, & feta cheese; still other times I make a light cream sauce with fresh tarragon - the sky's the limit!
Then just put the dish in a preheated 350-400 degree oven & bake for 20-30 minutes or until the fish is cooked through.