How to make
Defrost the fish, cut off the fins and remove the heads.
Remove the entrails and wash them thoroughly. Cut them into 3 cm wide pieces, but not all the way through.
For the fish marinade, peel an onion and cut it into thin crescents, add your favorite ketchup and mayonnaise. Add the juice of half a lemon and mix, add salt and sprinkle with black pepper, mix again.
Peel and cut the second onion into crescents, spread it out in the baking bag so that it forms a canapé.
Coat the fish generously with the marinade and place it on the canapé.
Tie the bag, pierce it with a skewer in several places and leave it like this for 30 minutes to marinate.
Place the bag n a tray and the tray in a preheated oven at 360°F (180°C).
Bake the fish for about 40 minutes, tearing open the bag for the last 10 minutes to bake the baked mackerel until it acquires a golden brown color.
The oven-baked mackerel in a baking bag is delicious for both lunch and dinner.
