Drain the mango on a sieve. Puree the mango, vinegar and oil. Peel fresh mango and cut it into slices from the stone. Finely dice the slices. Peel and finely chop the onion. Stir both into the mango puree.
Season with salt and pepper. Clean and wash the rocket. Clean, wash and cut the bell peppers into pieces. Heat 1 tablespoon of olive oil in a frying pan and fry the pepper pieces in it, remove.
Wash the fish, dab dry. Sprinkle with lemon juice and season with salt. Add 1 tablespoon of olive oil to the pan and fry the tuna steaks on both sides for 2-3 minutes. Arrange the rocket and peppers on plates.
Arrange mango puree and tuna on top. Sprinkle with red berries.