Season medallions on both sides with pepper and pumpkin pie spice. Heat oil in a large nonstick skillet over medium-high heat; brown pork on both sides, remove from pan, and reserve. Add onion and apples to skillet, sauté until soft. Add apple cider to skillet; heat to a simmer. Return pork medallions to pan, cover, and simmer for 5 minutes. Serves 4.