Take meat and trim away fat. Cut meat into 1-inch thick slices by cutting crosswise.
Take two pieces of plastic wrap for each slice of meat and place meat between them.
Press each slice into a 1/2-inch-thick medallion using the heel of your hand. Take plastic wrap and remove it from the meat.
Sprinkle salt and pepper lightly over the meat.
Coat a large nonstick skillet with cooking spray and heat over medium-high heat. Place meat on the heated skillet and cook about 4 to 6 minutes or until the meat is slightly pink in the center and the juices in the meat run clear. Turn the meat over once.
Remove the meat from the skillet and keep warm.
Combine the cranberry or apple juice, mustard, and cornstarch and add them to the skillet.
Mixture should be cooked stirring constantly until it becomes thick and bubbly. After mixture is thick and bubbly cook for an additional 2 minutes.