Put the veal tongue to boil with the vinegar and spices. You can also use a pressure cooker.
Take the ready tongue out, peel and cut it into pieces. Heat the oil in a pan and fry the onions. Add the chopped and peeled tomatoes, season with salt, black pepper, and a little tarragon to taste.
Boil the sauce until slightly thickened. In a greased pot, put the tongue, pour on the sauce, place the lid and bake it in a preheated moderate oven for about 1 hour.