Directions

1. To prepare brine: Place 1/4 cup brown sugar, salt and rosemary in a 9-by-13-inch baking dish. Pour in boiling water and stir to dissolve. Stir in ice cubes.
2. To butterfly & brine pork: You're going to double butterfly the pork loin so it can be flattened, stuffed and rolled. To do that, you'll make two long horizontal cuts, one on each side, dividing the roast in thirds without cutting all the way through. Place the roast on a cutting board. Holding the knife blade flat, so it's parallel to the board, make a lengthwise cut into the side of the roast just above the center, stopping short of the opposite edge so that the flap remains attached. Rotate the tenderloin 180 degrees . Still holding the knife parallel to the cutting board, make a lengthwise cut into the side opposite the original cut, just below the center, taking care not to cut all the way through. Open up the two cuts so you have a large rectangle of meat. Cover with a sheet of plastic wrap and pound to an even thickness of about 1/2 inch. Place the butterflied pork in the brine, adding more water to cover, if necessary. Cover and refrigerate for at least 2 hours and no more than 4 hours.
3. To prepare stuffing: Meanwhile, heat 1 tablespoon oil in a medium skillet over medium heat. Add pancetta (or prosciutto) and cook, stirring, until crisp, about 4 minutes. Transfer to a medium bowl along with any drippings from the pan. Stir in cranberries, breadcrumbs, 2 tablespoons brown sugar and rosemary. Refrigerate until ready to use.
4. Remove pork from brine (discard brine); rinse well and thoroughly dry with paper towels. Season the pork with 1/2 teaspoon pepper. Spread the cranberry stuffing over the pork. Roll tightly and secure in 4 places with kitchen string. Sprinkle with the remaining 1/4 teaspoon pepper.
5. Preheat oven to 375 degrees F. Line a rimmed baking sheet with foil.
6. Heat the remaining 1 tablespoon oil in a large skillet over medium-high heat. Add the pork; brown on all sides, turning often, 5 to 8 minutes total. Place on the prepared baking sheet.
7. Roast the pork, turning twice, until an instant-read thermometer inserted into the thickest part of the meat (not the stuffing) registers 140 degrees F, 45 minutes to 1 hour.
8. Transfer to a clean cutting board and let rest for 10 minutes. Slice and serve.