2-3poundsbeef top roundcut in 2 equal pieces (often labeled London Broil, but look for a thick one)
Sauce
½cupsour cream
½cupmayonnaise
2-3teaspoonslemon juicefresh
1garlic clovefinely minced or pressed
2tablespoonshorseradishmore if desired
kosher salt and black pepper to taste
1onionthinly sliced
soft white rolls or rye bread for serving
Instructions
Prepare sauce by whisking all ingredients together and refrigerate until ready to use. For best results, make at least a few hours in advance, or up to a couple of days ahead of time.
For beef, combine all spices and sprinkle on meat. Massage into all sides and then seal meat in a zip-top bag. Store in fridge for at least 24 hours, and up to 48 hours.
Let beef come to room temperature for 30 minutes before grilling. Heat grill to medium-high heat. Grill beef for 6-8 minutes on each side, or until thermometer registers about 135℉. If outside of beef is charring before inside is done, turn one side of grill off and place beef on indirect heat to finish cooking. When done, cover with foil and let stand for 10 minutes before slicing.
Slice beef as thin as possible. Spread sauce on each side of rolls or bread, pile on sliced beef, and top with sliced onions and more sauce if desired.