Season the skirt steak evenly on both sides with the salt, fresh ground pepper and arbol chili powder. Rub the seasonings into the flesh of the skirt steak.
Add the seasoned skirt steak to a small, shallow baking dish or a freezer bag. Pour in the whisky, lime juice and chopped cilantro.
Refrigerate for 2-3 hours or up to overnight.
Time saving tip: If you don’t have time to marinate the skirt steak in advance, season the meat and add it to a baking dish. Warm the whiskey and the lime juice in a small pan on the stove until simmering. Pour the whiskey mixture into the baking dish and sprinkle on the cilantro. Let marinate at room temperature for 20-30 minutes.
When ready to cook the fajitas, warm a cast iron or heavy bottomed sauté pan over high heat. Add one tablespoon of the avocado oil and warm the oil (saving half to cook the onions and peppers) for about 30 seconds until it looks slightly wavy in appearance. Add the skirt steak to the pan and discard the marinade. Sauté on high heat for about 2 minutes. Flip the steak and sauté the other side for an additional 2 minutes.
Remove the steak to a cutting board and tent with foil. Add the remaining 1 tablespoon of avocado oil to the pan and warm it up on medium-high heat. Add the onion and sauté 1 minute until softened. Add the pepper slices and a sprinkling of salt and sauté, along with the onions, until softened and slightly browned on the edges, about 4 minutes. Remove the pan from the heat.
To cut the steak, be sure to slice it against the grain. That means that whichever direction the fibers of the meat run, cut the meat perpendicular to those fibers and not parallel to them. If you cut meat against the grain, you will tenderize it by cutting through the tough fibers that run through the muscle of the meat.
Serve the fajitas with your favorite taco fixings.