Thaw the mackerel first, remove the head, entrails and fins. Cut into pieces.
Cut the onions in half rings, grate the carrots. Fry in vegetable oil until soft.
Put the fish on the onions, cover and cook over low heat for 10 minutes.
Season with salt and pepper to taste and add tomato paste.
Mix gently, cover and simmer another 15 minutes.
Braised mackerel is ready, sprinkle with herbs and serve with a side dish.