Lime Beef with Tortillas

4 medium limes
1/2 teaspoon salt
1/4 cup olive oil
12 corn tortillas
1 small onion
1/2 teaspoon crushed red pepper
4 small tomatoes
1 (1 1/2 pound) flank steak
2 medium avocados
1 teaspoon chili powder

About 5-6 hours before serving:

Grate peel and squeeze lime juice. Chop onion. In 13 x 9-inch dish, combine lime juice, lime peel, onion, chili powder, red pepper and salt. Add steak, turn and marinate for 4-5 hours, turning several times.

About 1 hour before serving:

Remove steak from marinade. Pour marinade into a 1-quart saucepan, heat to boil, boil 5 minutes and pour into small bowl. Beat with fork while adding olive oil in thin stream. Set aside.

Cut tomato wedges, cut avocados into thin wedge, and warm tortillas in oven.

Grill steak 5-10 minutes. Cut in thin diagonal slices.