Peel the apples and pumpkin and cut into large cubes. Finely chop the onion and garlic with a knife. Grate the lemon peel. Wash and gut the mackerel.
Pour vegetable oil into a hot frying pan and fry the chopped pieces of pumpkin and apple. Sprinkle with sugar and lemon zest.
Prepare the marinade: in a small container, mix soy sauce, juice of half a lemon, tomato sauce and spices. Coat the mackerel with marinade on all sides and grease it inside.
Place fried pieces of pumpkin and apple on the bottom of the baking dish, sprinkle with finely chopped onion and garlic on top and place mackerel carcasses on them, cut into strips of 3-4 cm, cover with foil and place in an oven preheated to 170° for 30 minutes.
Serve the baked mackerel, placing it on a wide dish, and next to it, place the vegetables on which it was baked as a side dish.