Puree all ingredients in a food processor. Transfer to a bowl. Can be made 2 hours in advance. Cover with plastic wrap and let stand at room temperature.
Rub meat all over with 2-3 tablespoons of chimichurri sauce and place in a ziplock bag to marinate. Save the rest to serve along side. Let marinate for 1 hour at room temperature or overnight in the refrigerator.
Preheat grill on medium high for 10 minutes.
Remove meat from bag and discard any extra sauce that was in the bag.
Place on grill for 4-5 minutes on a slant, then turn in the opposite direction to create
grill marks on the steak for 3 minutes. Flip the steak and repeat but for only 3 minutes in each direction. (medium-rare)
Remove the steak and cover with foil to allow the meat to rest and absorb its juices.
Serve with the remaining sauce.
(Credit: Eileen Forte, www.PaleoSimplified.com)