Instructions: Prepare chinichurri sauce; In food processor fitted with chopping blade, process onion and garlic until finely chopped. Add parsley and oil; process until pureed. Add lime juice, vinegar, salt and red pepper. Process just until mixed and set aside.

In shallow nonmetal baking dish or sealable large plastic food-storage bag, pour 1/2 cup chimichurri sauce. Set remaining sauce aside. Place steak in dish or bag; turn to coat with sauce. Cover dish or seal bag and refrigerate steak to marinate at leat 4 hours but no longer than 24 hours.

Pour remaining sauce into jar; cover and refrigerate to serve with steak.

Just before serfing, heat broiler or indoor grill. Remove steak from marinade and broil steak 3 to 4 inches from heat source 12 to 15 minutes for medium doneness, turning once. Discard marinade from dish or bag.

Transfer steak to serving platter; let stand 5 minutes. Cut crosswise into thin slices. Sprinkle with additional chopped parsley, if desired, and serve with remaining sauce.

NOTES : In Argentina, where outdoor grilling is a way of life, parsley-based chimichurri is the classic sauce cooks combine with beef, both as a marinade for grilling and as a sauce to serve with the meal. The sauce also makes a tasty marinade or topping for chicken or shrimp.

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