Beef and Avocado Fajitas

1 1/2 lb flank steak, trimmed if necessary
1 tablespoon ground cumin
1 tablespoon chile powder
3/4 teaspoon black pepper
3/4 teaspoon cayenne
1 1/2 teaspoons salt
1 heart of romaine
2 firm-ripe avocados (8 to 10 oz each)
12 (6-inch) flour tortillas (not low-fat)
1 cup loosely packed fresh cilantro sprigs

Heat a well-seasoned ridged grill pan (preferably cast-iron) over
moderately high heat until beginning to smoke, then brush with oil.
While pan heats, pat steak dry and stir together spices and salt,
then rub all over both sides of steak. Grill steak, turning over
once, 9 to 11 minutes total for medium-rare. Transfer to a cutting
board and let stand 10 minutes.

Meanwhile, cut romaine crosswise into thin shreds. Quarter avocados
lengthwise, then pit, peel, and cut lengthwise into 1/4-inch-thick
slices. While steak is standing, stack tortillas, wrapped completely
in dampened paper towels, on a microwave-safe plate and cook in a
microwave oven at high power (100 percent) until tortillas are hot,
about 1 1/2 minutes.

Holding knife at a 45-degree angle, thinly slice steak across the
grain. Serve with tortillas, avocado, romaine, cilantro, and your
favorite salsa.