Peel and finely dice the onions. Finely grate the bread. Knead minced meat, half of the onions, bread, egg and herbs well. Season to taste with salt and pepper. Cut mozzarella into cubes.
Form eight dumplings from the minced dough, pressing a cheese cube into the middle of each. Wash, quarter, seed and dice the tomatoes. Heat the oil in a pan and fry the dumplings well.
Take it out. Sauté the remaining onions in the frying fat and add the diced tomatoes. Fry briefly and deglaze with ketchup. Season to taste with salt and pepper. Wash basil, dab dry, cut into strips and sprinkle on top.
Add the dumplings to the tomato sauce and leave to stand for five minutes. Add the rest of the mozzarella to the sauce. Green ribbon noodles taste good with it.