Combine pineapple juice, sherry, teriyaki sauce, garlic and ginger. Marinate London Broil roast overnight, or two days for bolder flavor.

Preheat broiler or grill to high heat. Remove roast from marinade, reserving marinade. Pat roast dry, rub with oil, place on broiler pan and broil 15 minutes. Flip and broil an additional 15-18 minutes to 125°F. Allow to rest 10 minutes on cutting board tented with foil. London broil is ideal at medium rare to medium doneness (135°-145°F final temperature after resting).

Broil sliced pineapple and red onion if desired.

Bring reserved marinade to a boil in a saucepan, reduce to a simmer and reduce to 1/2-cup. Slice roast very thin against the grain, serve with warm sauce, pineapple and red onion.