Ingredients:

1 large onion, finely chopped
1/2 teaspoon ground cumin
4 garlic cloves, finely minced
1/2 teaspoon salt
Freshly ground pepper to taste
1 (12-ounce) bottle beer
1 (1 1/2 to 2-pounds) flank steak

Method:

1. Combine all ingredients, except steak, in a large zipper-style plastic bag, seal and shake to mix well.
2. Add steak to marinade, seal and refrigerate for several hours or overnight.
3. Heat gas grill on medium-high or charcoal grill until coals are ash white.
4. Remove steak from marinade, discarding marinade.
5. Grill steak for 4 to 5 minutes on each side or until desired degree of doneness
6. To serve, thinly slice steak diagonally across the grain.