Chop the onion, garlic and celery finely and cut the carrots into large wheels. Heat the oil and fry the onions and garlic first, then add celery and carrots. Season with spices and pour the canned tomatoes in.
Wait for it to boil for about 10 minutes. Put the cleaned mackerel in a greased tray and pour on the sauce . Wrap the tray with foil and place it to bake for 25 minutes. Then remove the foil and finish cooking for another 10 minutes.
Serve with torn up parsley (optional).