Trim fat from steaks. Place steaks on a baking sheet lined with parchment paper or plastic wrap.
For rub, in a small bowl combine the 1 teaspoon salt, the garlic powder, 1/2 teaspoon cumin, the chili powder, black pepper, and cayenne pepper. Sprinkle mixture evenly over both sides of each steak; rub in with your fingers. Cover with plastic wrap and marinate in the refrigerator for 1 hour.
For chimichurri, in a food processor or blender combine cilantro, parsley, vinegar, garlic, the 1/2 teaspoon salt, 1/2 teaspoon cumin, and the crushed red pepper. With processor or blender running, slowly add oil through opening in lid in a thin, steady stream until mixture is smooth. Set aside.
For a charcoal grill, grill steaks on the rack of an uncovered grill directly over medium coals for 7 to 9 minutes for medium-rare (145°F) or 10 to 12 minutes for medium (160°F), turning once halfway through grilling. (For a gas grill, preheat grill. Reduce heat to medium. Place steaks on grill rack over heat. Cover and grill as above.) Serve steaks with chimichurri.