Cook the gnocchi in salted water as indicated (about 3 minutes) and keep warm if necessary. Season the salmon cubes with lemon and pepper. Heat some olive oil in a deep pan or saucepan (not too hot) and fry the salmon cubes briefly until all pores are closed. Set aside in a small bowl.
Heat some fat again in the pan / saucepan, sauté the onion until translucent, add garlic if necessary (do not let it brown) and add the tomatoes. Reduce a little, season with Italian herbs, tomato paste, salt and pepper. Stir in the cream, stop boiling, and add the salmon cubes. Simmer for another 5 minutes. Just before serving, carefully fold in the rocket, keep a few leaves for decoration.