The big star of Tex-Mex cooking in the late 20th century—and the only example of the genre not likely to send cardiologists running screaming from the room—is fajitas. Fajita—the diminutive of faja, meaning sash or girdle—is the name applied by south Texas butchers to the diaphragm muscle of the steer, better known as skirt steak. (Real fajitas are always made with skirt steak—not with chicken, shrimp, or, Lord help us, portobello mushrooms!) The celebrated original Ninfa's restaurant in Houston claims to have introduced the dish in restaurants in 1973. But according to Texas A&M animal science lecturer Homero Recio, who has studied the origins of fajitas, that honor belongs to the Round-Up Restaurant in Pharr, a few miles from the border in far south Texas, whose fajitas first appeared in 1969. The Round-Up may also have been the first place to serve the meat on a sizzling platter (the accompanying onions, peppers, and tomatoes were added later), though that distinction is claimed by others, too, among them the Cortez family, who opened a place called La Margarita a block from Mi Tierra in 1981, with fajitas as the featured item. The fajitas at La Margarita are flawless, in any case—tender and flavorful meat with just the right proportion of vegetables.