Preheat oven to 500°.
Rub butter over surface of tenderloin; sprinkle with salt and pepper. Place tenderloin on a lightly greased rack in a shallow roasting pan. Turn narrow end under to make roast more uniformly thick. Insert meat thermometer, if desired.
Place in oven, and immediately reduce temperature to 400°. Bake, uncovered, for 50 minutes or until meat thermometer registers 140° (rare).
Cut tenderloin into 1-inchthick slices and arrange on a heated platter. Serve with Sherry- Mushroom Sauce.
Note: Tenderloin may be garnished with tomato roses.