Sweat the chopped onions in oil, add the tomato paste, roast briefly, then add the tomatoes and pizza tomatoes, season with salt and pepper and reduce a little. Twist small balls out of the sausages and let them steep in the sauce.
In the meantime, prepare the gnocchi according to the instructions on the packet (or make them yourself).
Then either:
Carefully mix the sauce and gnocchi together, sprinkle with chopped basil and serve. Put the cheese on the table.
Or:
Carefully mix the sauce and gnocchi together, sprinkle with the grated cheese and bake in the oven for 20 minutes.