fifteen years ago, fajitas were "discovered." since then, an awful lot of good meat has been wrecked, and skirt steak-once a "grinder" item-has risen sharply in price. Because skirt doesn't come from a "tender quadrant" of the carcass, some care is needed to turn it into good food. First, it needs to be marinated to tenderize and flavor it.
Mix all the ingredients together, except the meat, to make a marinade. Pour over the skirt steak, in a non-reactive container (not metal), cover, and stir occasiionally for six to eight hours.
Fajitas can be cooked in several ways. If you have the space, smoke the fajitas for 30 minutes with pure mesquite smoke, and then cook for 4-7 minutes per side over direct heat-mesquite coals being the heat of choice. Baste with the marinade throughout the cooking process. If you need to cook completely over direct heat, then use a fairly slow fire, about like you should use when grilling chicken, and cook, covered if possible, for about 10 - 15 minutes per side, basting with the marinade.
Figure about a half pound of meat and 3 to 4 tortillas per person. When slicing fajitas, you'll notice that the grain of the skirt steak all runs the same way. If you'll slice the skirt at a forty-five degree angle to the grain, and hold your knife on a forty-five degree angle as well, you'll find that the fajitas are much more tender! Serve the fajitas with flour tortillas, pico de gallo salsa, guacamole, and cold beer. You'll notice that I didn't say anything about chicken fajitas-that's a contradiction in terms.