For the beef cutlets, pound the cutlets, salt, rub one side with mustard. Fry well in olive oil on both sides, remove from the pan.
Fry finely chopped onions in the frying residue until golden, tomato, dust with flour and pour in soup and season.
Put everything in a casserole with a lid and braise in the oven at 160 °C for 45 minutes, remove the meat from the casserole and mix with crème fraîche.
Put the cutlets on the plate in the sauce and serve.