A wonderful recipe with red wine!
Put the tongue in cold water, bring to a gentle simmer and simmer for 3-4 hours. Remove the skin and cool in the clear soup (for later use) or slice as desired. For the sauce, melt the butter in a heavy casserole, pour in the onions and saute over very low heat until golden. Stir in the flour with a wooden spoon. Later, add the juice of one lemon and the beef broth and stir until smooth. Put the lid on and simmer the sauce at low temperature. In a small saucepan, heat the vinegar. Pour in the sugar and cook, stirring continuously, over high heat for 5-6 min until a thin syrup is formed. Add the syrup by the spoonful to the sauce form, stirring constantly to combine the flavors. season with pepper.
If the sauce is not tart enough, add additional juice of one lemon at a time, if desired. Mash the sauce. If the tongue is still hot enough, place the tongue slices on a preheated serving platter and top with the sauce. If the tongue is already cooled, place the slices in a saucepan, pour the sauce over them and warm the dish at a low temperature for 5-10 min.
ready sauce warmed.