Place the flank steak in a zip lock bag then add the garlic, cumin, scallion, olive oil, paprika, salt and pepper. Marinade for at least 1 hour or overnight.
Remove steak from marinade bag and remove as much of the marinade as possible. Discard remaining marinade.
Place the steak on the preheated grill and cook 5 minutes on each side for medium doneness or cook until desired degree of doneness.
Place all the ingredients in a food processor and process until smooth.