2 tablespoons finely chopped cilantro

1 jalapeno chile, seeded, finely chopped, or 1 tablespoon store-bought spicy green salsa

1/2 teaspoon ground cumin1 tablespoon fresh lemon juice

1/2 teaspoon salt

1/4 teaspoon black pepper

1 ripe medium avocado, peeled, pitted, and finely chopped

1. Place all the marinade ingredients in a large nonaluminum mixing bowl and whisk until combined. Taste for seasoning. Place the skirt steak in the mixing bowl, being sure to flatten it out and turn it well to coat all sides with marinade. Marinate for 2 to 4 hours covered in the refrigerator.

2. Meanwhile, mix all the salsa ingredients but the avocado in a mixing bowl. Just before serving add the chopped avocado, taking care to keep the avocado in pieces by mixing carefully. Taste for seasoning.

3. Prepare a barbecue for medium-heat grilling. Remove the steak and the onion slices from the marinade and grill 3 inches from the heat for 4 to 6 minutes on each side for medium-rare. Use a grill pan with holes to grill the onion slices, so they don't fall through the grill, and grill until they are lightly charred and soft.

4. Place the steak and onions on a carving platter, let rest for 10 minutes and then thinly slice the meat on the diagonal. Spoon some of the salsa on top of the sliced meat and Serve the remaining salsa and the warmed tortillas on the side.

Advance preparation: Can be prepared up to four hours ahead through Step 2 and refrigerated.

(Diane Rossen Worthington is an authority on new American cooking. She is the author of 18 cookbooks, including "Seriously Simple Parties," and a James Beard Award-winning radio show host. You can contact her at www.seriouslysimple.com.)