Dice the onion and sauté in one tablespoon of warmed olive oil until golden brown.
Chop the tomatoes at random and finely chop the garlic. Add vegetables to the pan, season and fry for about 10 minutes over low heat until the tomatoes are softened. Make sure that they do not completely lose their shape, otherwise the sauce will not turn out very beautiful.
Season the steaks and brush with olive oil, fry in a pan or grill for one minute on each side.
Place fish and tomatoes on plates and sprinkle with finely chopped onions.