Sauté the onion in an oiled pan, add the tomatoes and basil and simmer for 5 minutes. Add 2 - 3 tablespoons of water, sugar, vinegar, salt and pepper and simmer for 3 - 4 minutes. Now strain the onion, tomato and basil sauce through a sieve. Season the sauce to taste and season it if necessary.
Knead the ground beef with the onion, herbs and a little salt and shape into dumplings.
Melt the butter in the pan and fry the dumplings all around and keep warm. Pour the fat out of the pan and bring the tomato sauce to the boil.