Sauté for 5 minutes. Add the tripe and let it brown for another 5 minutes (7). Then add the tomatoes (8) and water, using the same bowl that contained the tomatoes (9). Season with salt.

Put the tripe into a saucepan with a quarter cupful of water, with the lid on, place on the hob for 8-10 minutes approx. Discard the liquor in the pot, add the sliced onion and cover with cold milk.