For the tomato sauce, peel onion and garlic. Chop onion finely, crush garlic finely. Heat 1 tablespoon of oil in a saucepan. Fry onion and garlic in it. Stir in tomato paste, sweat briefly.
Deglaze with chunky tomatoes and vinegar, bring to the boil and simmer covered for about 5 minutes. Season to taste with salt, pepper and sugar.
In the meantime, dab the escalopes dry, cut them into 3 pieces each and tap them thinner. Grate the Parmesan finely and mix with breadcrumbs. Whisk the eggs in a deep plate and season with salt and pepper.
Bread the schnitzel. Heat 6-8 tablespoons of oil in a frying pan in portions. Fry the escalopes in it in 2-3 portions at medium heat on each side for about 2 minutes. Drain finished cutlets on kitchen paper.
Heat the sauce again briefly. Wash basil, shake dry, pluck leaves from the stalks and chop. Stir the basil into the sauce. Serve everything.