In a small bowl, combine all the spices for the dry rub. Cover the flank steak on all sides evenly with the dry rub. Place steak in a Ziploc bag and marinade in the refrigerator for at least 3 hours but overnight is ideal!

Add all the ingredients, except the olive oil, for the chimichurri sauce to the bowl of a food processor. Turn the food processor on and slowly add in the olive oil through the opening of the food processor lid. Process until the mixture is well combined, approximately 30 seconds. Remove from processor and store in an airtight container in the refrigerator until ready to serve.

When you are ready to cook the steak, heat the grill or a grill pan over medium-high heat. Remove the steak from the bag. Add the steak to the hot grill or grill pan, and cook on each side for approximately 2-3 minutes for medium-rare to medium doneness.

Remove steak from grill to a cutting board. Cover in foil and allow to rest for at least 10 minutes. Slice and serve with the chimichurri.