Cut zucchini into slices, dice tomatoes, fry both in 1 tablespoon oil for approx. 1 minute. Season, take out. Dice the cheese, cut the salmon in half crosswise, season. Place the lower half of the salmon in a greased dish, spread the zucchini-tomato-vegetables with cheese on top, place the 2nd half of the salmon on top, cover with flakes of butter and cook in the oven preheated to 200 degrees for about 25 minutes.
Quarter the potatoes and cook in salted water for 15 minutes. Pluck the rosemary. Heat the rest of the oil in a pan, toss the potatoes with rosemary in it.