Combine beer, onions, garlic, lime juice, cilantro, red pepper flakes and salt; reserve 1 cup. Pour remaining marinade over steaks. Cover and refrigerate overnight.

Remove steaks from marinade; discard marinade. Grill steaks to desired doneness, turning once. Keep warm.

For each serving: Slice 3 oz steak into thin strips; brush lightly with reserved marinade. Arrange steak strips, 1 oz lettuce and 2 oz salsa onto warm tortilla; plate. Garnish with avocado slice, chili pepper and cilantro sprig.

Courtesy of National Cattlemen's Beef Association