Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
                        -----marinade-----
   1      medium        onion -- thinly sliced
     1/4  cup           cider vinegar
   3      tablespoons   fresh rosemary
   2      tablespoons   fresh sage -- minced
   1      tablespoon    fresh parsley -- chopped
     2/3  cup           balsamic vinegar
                        juice from 1/2 lemon
   1      tablespoon    pink peppercorns
     1/2  cup           extra-virgin olive oil
                        -----tenderloin-----
   1 1/2  pounds        boneless pork tenderloin
   2      tablespoons   olive oil -- divided
                        salt and pepper to taste
     2/3  cup           dry white wine -- divided

Preparation:

For the marinade: In a skillet, combine onion and cider vinegar and simmer until the onion is soft. Add rosemary, sage, parsley, balsamic vinegar, juice of 1/2 lemon, pink peppercorns and extra-virgin olive oil. Stir well, remove from heat and set aside. Preheat the oven to 375F. Pat pork with paper towels and rub it all over with 1 Tbl of olive oil. Sprinkle with salt and pepper to taste. In a frying pan, heat 1 Tbl olive oil over medium high heat and brown the meat on all sides. Transfer the meat to a baking dish and add 1/3 cup dry white wine to the dish. Roast for 20 to 25 minutes, or until cooked to 155F to 160F. Midway through the cooking add another 1/3 cup wine to the pan. Transfer the meat to a deep non-metal dish just large enough to hold it. Pour the marinade over the meat, and let it marinate, covered, in the refrigerator for at least 3 hours, or up to 3 days. Bring the meat, in the marinade, to room temperature before serving. Cut it in thin slices, arrange on a serving platter, and spoon some of the marinade over the slices. Of course this dish can also be reheated in the marinade and served warm. Source: CIAO ITALIA by Mary Ann Esposito