How to Make It
In a large pot, combine the onion, carrot, celery, garlic, parsley, bay leaf, wine and 12 cups of water. Add 1 tablespoon of salt and 1/2 teaspoon of pepper. Add the tongue and bring to a boil. Simmer over moderately low heat until tender, about 2 hours. Remove the pot from the heat and let the tongue stand in the liquid until slightly cooled, about 45 minutes. Using a paring knife, peel and trim the tongue. Wrap tightly in plastic wrap and refrigerate until chilled, at least 45 minutes.
Meanwhile, in the bowl of a food processor, combine the tuna with the anchovies, capers and lemon juice and process until finely chopped. Add the oil and mayonnaise and process until smooth and thick. Season with salt and pepper. Scrape the sauce into a bowl, cover with plastic wrap and refrigerate until chilled, about 20 minutes.
Slice the tongue crosswise into 1/3-inch medallions and transfer to plates. Spoon some of the sauce over the tongue medallions and garnish with the olives and parsley. Serve with lemon wedges, the rest of the sauce at the table.