Season the pork with the salt, rubbing it into the meat, and place the sage leaves around the loin, secured under the twine. Set aside for 30 minutes.
Mince together the pancetta, garlic and parsley to form a homogenous, smooth mixture. In a large, cast-iron casserole or Dutch oven, heat the olive oil and add the pork paste, cooking until it has melted into the oil. Place the pork in the pan and brown on all sides so that a uniform crust is formed. Add 1 cup red wine and reduce by 3/4. Add the remaining cup of wine and the tomatoes, cover, and bring to a low simmer. Cook for 2 hours, until meat is fork tender.
Remove meat from casserole, allow to rest 15 minutes, and remove string and sage leaves. Serve in 1/3-inch thick slices.
Recipe copyright 2000, Mario Batali. All Rights Reserved.