If the skirt steak arrives in one long strip I will usually cut it into smaller, more manageable pieces. You can optionally pound the steak thinner if you want a more even cut. I usually cover it in parchment paper and pound it down with a cast iron skillet.
Give the steak a healthy sprinkling of salt on both sides.
Combine the chile powder mixture in a small bowl. Keep in mind that you can use any chile powder combo that sounds appealing to you. I used 2 teaspoons New Mexican chile powder, 2 teaspoons Chipotle powder, 1 teaspoon Ancho powder, 1/2 teaspoon salt, and some freshly cracked black pepper.
Rub some oil into both sides of the skirt steak, then coat each side of the steak with the chile powder mixture -- I usually use my fingers to rub it in.
Preheat a cast iron skillet if available. I used just over medium heat for this batch. Cook each steak for 2-3 minutes per side or until the inside temp registers 130-135F. Once cooked set aside, cover with foil, and let it rest for a few minutes.
If you want to make the Salsa de Aguacate, combine the following ingredients in a blender or food processor: the flesh of a ripe avocado, 1/4 cup water, juice of 1 lime, 4-5 sprigs of cilantro, 1/2 peeled garlic clove, and 1/4 teaspoon salt. Combine well, adding additional splashes of water if necessary.
For tacos I highly recommend crisping up the tortillas first -- add corn tortillas to a dry skillet over medium-high heat along with strips of cheese on each tortilla. Cook for 1-2 minutes or until light brown spots are forming on the underside of the tortillas.
Once the steak has rested, cut it against the grain into thin strips. You can optionally cut the strips into bite-sized pieces.
Each cheesy tortilla gets Carne Asada, Salsa de Aguacate, and Pickled Onions (optional). Serve with lime wedges for a final, optional squeeze of lime on each taco.