Wash the cod, dab dry and cut into large cubes. Sprinkle fish with lemon juice and sprinkle with salt. Leave to stand for about 10 minutes. Meanwhile clean, wash and dry the rocket and tomatoes.
Cut tomatoes in half, rocket, except for a few leaves, cut into strips. Peel onion and garlic. Cut onion into fine slices, press garlic through a garlic press. Drain the cod.
Heat clarified butter in a pan and fry the fish in it until golden brown. Remove the fish cubes. Sauté the onion and garlic in hot frying fat until transparent, add the tomatoes and strips of rocket and toss briefly.
Sprinkle with vinegar and olive oil and season with salt and pepper. Put them on a plate together with the warm fish cubes and serve garnished with the rocket leaves and lemon wedges. Fresh baguette tastes good with it.