Place all ingredients (except steak) in a food processor. Pulse until a smooth sauce is achieved.
Refrigerate if time permits. (Can be made one day ahead.) Bring to room temperature before using.
Sprinkle both sides of steaks with salt and pepper.
Place steaks on hot grill pan or barbeque grill, pre-heated to high, and cook until desired wellness (about 3 minutes per side for medium-rare).
Slice steaks crosswise and arrange on a platter.
Spoon chimichurri sauce over the steaks and serve.