Mackerel rinse, dry. Mix juice of one lemon, kitchen herbs and oil.
Brush the fish with the mixture and let it marinate for about 1 hour.
Clean and rinse fennel and cut into wedges. Season fish with salt and place in a roasting pan. Add fennel, diced onion and garlic and tomatoes with liquid. Season. Roast at 200 °C for about 25 min. Serve with buttered potatoes.