London Broil is actually a cooking style that involves marination and broiling (or grilling). First you should score the meat lightly with a sharp knife to allow some of the marinade to get into the meat, then marinade form 2-8 hours. Broil or grill the meat to the proper internal temperature (see below), let it rest for 10 minutes and slice thinly across the grain. This cooking style works well for this cut, Flank Steak, Skirt Steak and Hanger Steak.
This cut should be cooked using an internal meat thermometer that is oven safe, no matter the method of cooking. These devices cost $20 and are critical for the best eating experience and are as useful a tool as a spatula. The internal Fahrenheit temperature goals are: 115-120 Extra-Rare (Bleu); 120-125 Rare; 125-130 Medium Rare; 130-135 Medium. Not recommended to go above 135 degrees.
Cibola Farms London Broil is a cut of meat from the top round. “London Broil” is an American (not English) style of cooking meat by marinating it for a number of hours, then grilling or broiling and slicing thin across the grain. The top round is well suited for this cooking style and thus the connection to the name.