Cut tenderloin into 8 pieces; place each piece between 2 pieces of plastic wrap or waxed paper and flatten to 1/2-in. thickness. Sprinkle with lemon pepper. , Melt butter in a large skillet over medium heat; cook pork until a thermometer reads 145°, 3-4 minutes on each side. Remove to a serving platter and keep warm. , To the pan juices, add lemon juice, Worcestershire sauce and mustard; heat through, stirring occasionally. Pour over the pork and if desired, sprinkle with parsley.