3 tablespoons butter
2 8- to 10-ounce pork tenderloin
1 cup chopped onion
2 tablespoons chopped fresh rosemary
1 cup canned low-salt chicken broth
3/4 cup canned whole berry cranberry sauce
2 tablespoons balsamic vinegar
Preheat oven to 450 °F.
Melt 1 tablespoon butter in heavy large ovenproof skillet over medium-high heat. Sprinkle pork with salt and pepper. Sear pork on all sides, about 2 minutes. Place skillet with pork in oven. Roast pork until thermometer inserted into center registers 155 °F, about 10 minutes.
Meanwhile, melt remaining butter in heavy medium skillet over medium-high heat. Add onion and rosemary; sauté over medium heat until onion is tender, about 3 minutes. Add broth, cranberry sauce and vinegar and whisk until cranberry sauce melts, about 3 minutes.
Transfer pork to a warm plate. Scrape any juices from large skillet into cranberry mixture.
Boil until sauce has reduced enough to coat spoon thickly. Season with salt and pepper. Slice pork and serve with sauce.