How to make
Clean and wash the fish and season it with salt and black pepper.
Stuff the fish with the frozen vegetables (grab a package of your choice, you can also use fresh ones).
Stew the onion, carrot and tomato in a pan and season them.
Grease the bottom of the baking pan, pour most of the stewed stuffing, add the mackerel on it and arrange the chopped mushrooms around it.
Place the remaining vegetables and lemon slices on top of the fish.
Cover with foil and bake the fish at 480°F (250°C) for 15 minutes, then at 390°F (200°C) for 30 minutes.
The delicious baked mackerel with vegetables is ready.