Arrange beef, mushrooms, potatoes, tomatoes and onions on a lettuce-lined platter. Position base of fondue pot in center of table. Heat oil in pot on stove over medium heat to 375° or until a cube of bread browns quickly. Light Sterno in base of pot; place pot over base. (If using electric pot, use the base to heat the oil.) Spear beef and vegetables with fondue fork; cook in hot oil to desired doneness. Serve with desired sauces.
HORSERADISH SAUCE: In a small bowl, thoroughly combine 1/2 cup sour cream, 2 tbsp. prepared horseradish and 2 tsp. lemon juice. Makes 1/2 cup.
Good to Know: Packaged Peppercorn or Béarnaise Sauce Mix can be used to create a convenient sauce to serve with fondue.