Finely chopped onion stew in part by vegetable oil until soft. Add a soft tomato, chopped and stewd to Braising, then strain through a sieve. In a deep dish put the remaining tomatoes - whole and are covered with smashed tomatoes, mixed with finely chopped leaves of celery and parsley. Once the sauce boil, add the flour, fuzzy milk, remaining oil and salt. The dish is left to simmer on low heat. For flavor can add a little red wine or cognac.