For the Meat: Choose beef labeled London Broil, Top Round Steak, or Flank Steak. For Marinade: Pineapple juice helps to tenderize the meat while the other ingredients add flavor.
In a medium bowl whisk together the pineapple juice, oil, soy sauce, Worcestershire sauce, red pepper flakes, and dried minced onion together.
Place the meat into a large storage bag and pour the marinade over the beef. Seal and toss to coat the meat in the marinade. Refrigerate for at least 2 hours or up to 24 hours.
When ready to cook, remove the beef from the marinade, letting the excess marinade drip away, and place it onto a sheet pan. Discard the marinade.
Broil for 5 minutes. Flip the meat and return to the oven and broil for 3-4 minutes, or until the internal temperature reaches 130 degrees Fahrenheit.
Remove the meat from the oven and allow to rest for 10 minutes. To serve, cut the London Broil against the grain into very thin slices.