Mix mayonnaise with ketchup, add ground pepper to taste.
Mix well until smooth and add the garlic passed through the press and mix again.
Cut the onions into rings.
Cut the fish along the ridge and remove the bones, cut another into pieces. Season to taste and lay the hake on the frypot covered with foil.
Put the onions on the fish.
Then grease with the previously prepared sauce.
Cover the fish tightly with foil.
Bake hake with sauce at 180 degrees 40 minutes.
Serve baked hake with sauce along with the sauce with any side dish.