Ingredient note: London broil is a thicker cut of steak that benefits from the tenderizing effects of a marinade.Tip: A ridged grill pan is great for indoor grilling, but you can use the broiler or, if weather permits, cook the steak on an outdoor grill.
Whisk wine, vinegar, cherry preserves, garlic, salt and pepper in a small bowl. Place meat in a shallow glass dish. Pour the marinade over the meat and turn to coat. Cover and marinate in the refrigerator, turning several times, for at least 20 minutes or up to 8 hours.
Remove the meat from the marinade. Pour the marinade into a small saucepan; add shallot and set aside. Brush a ridged grill pan (see Tip) or heavy skillet with oil; heat over medium-high heat. Add the meat and cook for 10 to 12 minutes per side for medium-rare, depending on thickness, or until it reaches desired doneness. (It may appear that the meat is burning but don't worry, it will form a pleasant crust.) Transfer the meat to a cutting board; let rest for 5 minutes.
While the meat is cooking, bring the marinade to a boil; cook over medium-high heat for 5 to 7 minutes, or until it is reduced to about 1/2 cup. Remove from the heat; add butter and whisk until melted.
Slice the meat thinly against the grain. Add any juices on the cutting board to the sauce. Serve the meat with the sauce.