Preheat a gas grill to medium-high. Lightly score steak; season with salt and pepper.
Pulse oil, onion, garlic, capers, parsley, lemon juice, crushed red pepper and anchovy, if desired, in a food processor. Season with salt and pepper.
Grill steak 4 to 6 minutes per side for medium-rare. Let stand for 5 minutes.
Thinly slice steak against the grain and serve, passing sauce on the side.
This recipe was previously published in All You, Back to School Special, July 2013.
Find recipes with ingredients that you have on hand.