Wash and clean the tomatoes and carve the tomato skin crosswise once. Put the tomatoes in boiling water for 1-2 minutes. Remove, rinse with cold water and peel skin. Cut tomatoes into quarters, remove seeds and dice flesh. Peel and finely dice onions and garlic
Heat 4 tablespoons of oil in a large pot. Fry the onions and garlic until transparent. Sprinkle sugar over it and let it caramelize slightly. Add tomato paste and briefly sauté. Deglaze with vinegar and add tomatoes. Season with salt and pepper. Simmer over medium heat for 20-30 minutes (depending on the desired thickness of the sauce), stirring frequently. Wash the basil, shake dry. Pluck leaves and chop finely. Set aside a little bit for sprinkling, stir the rest into the sauce
Wash the peaches, carve the skin crosswise with a knife. Place in boiling water for 1-2 minutes, remove, rinse with cold water and peel off skin. Cut the flesh from the stone. Cut 1/4 peach into wedges and 1/4 peach into small cubes. Cut the rest of the peach into small cubes and add to the sauce. Puree the sauce, stir in Prosecco until the desired consistency is achieved. Bring everything to the boil again and season to taste. Serve garnished with peach slices and cubes and basil