1. Let steak stand 30 minutes at room temperature. Sprinkle steak with 1/2 teaspoon pepper and salt.
2. Preheat grill to high heat.
3. Place garlic in food processor; process until minced. Add parsley, cilantro, and mint; process until coarsely chopped. Add oil, next 3 ingredients (through capers), and remaining 1/2 teaspoon pepper; process until finely chopped.
4. Place steak on grill rack coated with cooking spray. Grill 2 minutes; turn steak over. Grill 2 to 3 minutes or until desired degree of doneness. Let stand 5 minutes. Cut steak across grain into thin slices. Serve with sauce.
Kids Can Help: Like with most of my sauces, kids can do practically all the work. They can pick the stems off the herbs or use a child-safe knife to cut them. Kids can also measure out all the ingredients and dump them directly into the food processor.