Wash, sour and salt the fish and place in a greased baking dish. For the sauce, finely dice the garlic and onions and sauté in the olive oil. Peel and dice the tomatoes and add to the onions and garlic with the parsley and oregano. Season the sauce with salt, pepper and sugar, spread over the fish and bake in the oven at 200-225 ° C for 25-30 minutes.