Flank steak, also known as London broil, isn’t the most tender cut of beef, but it is one of the most flavorful. The key to getting a tender flank steak is to let the meat marinate for a good, long time—in this case, in a mixture of red wine, Worcestershire sauce, garlic, various spices, and fresh rosemary—and then carve it across the grain into thin slices before serving.