Trim fat from pork. Cut pork crosswise into 1-inch-thick slices. Place each slice between 2 pieces of plastic wrap. With the heel of your hand, press each slice into a 1/2-inch-thick medallion. Remove plastic wrap. Sprinkle lightly with salt and freshly ground black pepper.
Coat an unheated large nonstick skillet with cooking spray. Heat skillet over medium-high heat. Add pork; cook for 6 minutes or until pork is slightly pink in center and juices run clear, turning once. Transfer to a serving platter; keep warm.
Combine cranberry juice, mustard, and cornstarch; add to skillet. Cook and stir until thickened and bubbly. Cook and stir for 2 minutes more. Stir cherries into mixture in skillet. Serve over pork. Makes 4 servings.