Combine the olive oil, soy sauce, Worcestershire sauce, lemon juice, lemon zest, garlic, Italian seasoning, red pepper flakes, black pepper, salt, onion powder, and smoked paprika in a mixing bowl or resealable plastic bag. Whisk together until well-mixed.

Place the London broil in the marinade, ensuring it is fully coated. Refrigerate and allow the meat to marinate for a minimum of 2 hours, though marinating for up to 24 hours will yield enhanced flavor.

Broiling Method: Preheat the broiler to a medium-high setting (450°F). Lightly coat a sheet pan with cooking spray, then place the marinated meat on the pan. Broil the steak for approximately 7 minutes per side, or until a thermometer inserted into the thickest part reads 135-140°F. Cooking times may vary depending on the meat’s thickness.

Grilling Method: Preheat a grill or grill pan to medium-high heat. Place the marinated London broil on the grill and cook for around 7-8 minutes per side, or until the internal temperature reaches 135-140°F. Adjust cooking time based on the thickness of the meat.

Once cooked, remove the meat and allow it to rest for 5-7 minutes. Slice the London broil thinly against the grain and garnish with fresh parsley before serving.