Pat the London broil dry
Season both sides with salt, pepper, garlic powder, and onion powder
Optional: marinate for 4 to 24 hours in oil, soy sauce, vinegar, garlic, and Worcestershire sauce
Preheat the broiler or grill to high heat
Place the meat on a broiler pan or hot grill
Cook 4 to 6 minutes per side for medium-rare, depending on thickness
Check for an internal temperature of 130 to 135°F for medium-rare
Remove from heat and let rest for 10 minutes
Slice thinly against the grain
Serve immediately