Arrachera beef is a savory Mexican specialty that may have originated with vaqueros driving their herds to south Texas in the 1930s. Tex-mex cooks eventually reinterpreted arrachera beef, or "arracheras," as the beef fajitas frequently on menus in U.S. restaurants. Two things distinguish arrachera beef from other preparations: it must be made from skirt steak, a cut from the belly, and the meat must undergo a lengthy marination -- usually with a concoction that includes citrus juice, garlic, chiles and onions. They're best grilled over an open flame. Serve arrachera beef as you would fajitas, with tortillas and toppings of your choice.
Trim the fat from the skirt steak. If you're working with a large piece of skirt steak, you may wish to cut it into sections for easier grilling.
Combine the citrus juice, garlic, onion, chiles, vegetable oil, salt, pepper and liquid smoke, if using. For a 1-lb. skirt steak, use 1 cup orange juice or ½ cup lime juice, 2 tbsp. minced garlic, ½ onion, 1 tbsp. liquid smoke and 1 chile -- or more, if you like it extra spicy. Add salt and pepper to taste.
Place the skirt steak in the marinade and place in the refrigerator overnight, or up to three days.
Bring the skirt steak to room temperature before grilling.
Heat the grill to high heat, or preheat your oven broiler to 500 degrees Fahrenheit.
Cook the skirt steak 4 to 5 minutes on each side, until the meat is nicely browned. Arrachera beef is normally served with a little pink inside -- medium -- but you can adjust the cooking time up or down to your taste.
Remove the meat to a cutting board, cover with foil and allow it to stand 5 minutes. Slice the steak across the grain into thin strips, or cut into ½-inch cubes; serve.