Cut tenderloin crosswise into 8 medallions, about 3/4-inch thick. Season both sides of medallions generously with black pepper and set aside.
Melt butter in large heavy skillet over medium-high heat; sauté onion until soft, about 2-3 minutes. Add medallions, brown on one side, about 3-4 minutes. Meanwhile, in small bowl stir together brandy, broth, cherries, mustard and soy sauce. Turn medallions, add brandy mixture to skillet, bring to a boil, then lower heat to a simmer and cover. Cook undisturbed for 6 minutes. Uncover, stir in preserves and cook and stir until sauce is slightly thickened. Serve medallions with pan sauce.
