Give the skirt steak a sprinkling of salt on both sides. If it arrived 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. If you don't have a meat pounder you can easily do this with a skillet. I usually put plastic on either side of the meat before pounding.
For the marinade, add the listed ingredients to a blender and combine well.
Create a single layer of steak in a casserole dish. Cover with the marinade and be sure to get some underneath as well. Cover with plastic and marinate in the fridge for an hour or so. (You could alternatively use a Ziploc bag.)
For the Pico de Gallo, start by giving the tomatoes, jalapeno, and cilantro a good rinse. Peel the onion and de-stem the tomatoes and jalapenos. I usually twist off and discard the bottom, thicker portions of the cilantro stems, but keep the upper portion of the stems that hold the leaves together.
Finely chop the tomatoes, onion, and jalapeno into 1/4" sized chunks. Finely dice the cilantro. For a milder version you can start by using only 1 of the jalapenos and adding more incrementally if you want more heat. Combine everything in a mixing bowl along with 1/2 teaspoon of salt and the juice of two limes. Mix together well and taste for seasoning. Add additional salt and lime if necessary (I added more salt to this batch).
Preheat the grill so it's piping hot before you add the steak. I usually pat the meat dry before adding to the grill. Cook each piece of meat for 2-3 minutes per side or until the internal temp is 130-135F (medium-rare). You can always cook them longer if that's your preference, but skirt steak will toughen up a bit at higher temps.
Let the cooked meat rest for 5-10 minutes before slicing. Cut against the grain into thin strips. For tacos I will usually cut the strips into bite-sized pieces.
For serving, heat up the tortillas in a dry skillet over medium-high heat. Add cheese to each tortilla and cook until they are crisping up and light brown spots are forming on the underside.
Each cheesy tortilla gets Carne Asada, Pico de Gallo, and a final squeeze of lime. Buen Provecho!