1 1/2 tbsp. butter
1 (8 to 10 oz.) pork tenderloin
1/2 c. chopped onion
1 tbsp. chopped fresh rosemary
1/2 c. canned low-salt chicken broth
1/3 c. canned whole berry cranberry sauce
1 tbsp. balsamic vinegar

Preheat oven to 450°F. Melt 1/2 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 1 tablespoon butter in heavy medium skillet over medium-high heat. Add onion and rosemary; saut until onion softens, about 3 minutes. Add broth, cranberry sauce and vinegar and whisk until cranberry sauce melts, about 2 minutes. Transfer pork to work surface. Scrape any juices from large skillet into cranberry mixture. Boil until sauce has reduced enough to coat spoon thickly, about 6 minutes. Season with salt and pepper. Slice pork and serve with sauce.