Place skirt steak on a cutting board, remove the top fat and silver skin, top with a plastic sheet, and pound the meat with a mallet on both sides until it is about ¼-inch thick (0.5 cm). Slice the steak into 3 to 4 pieces to fit in into the skillet where it will cook.
Then, combine the taco seasoning, olive oil, and lime juice in a large Ziploc bag and place the steak inside. Shake to combine!
Next, squeeze the air out of the bag, seal, and let the skirt steak marinate at room temp for 20 minutes maximum. If you marinate longer, the meat flavors may get lost.
Remove the steak from the bag. Then dab to remove excess moisture from the marinade. This is so the steak can properly sear and get a nice brown crust.
Cook the skirt steak either on a charcoal grill (preferred) or in a large cast-iron skillet or griddle. To cook it indoors, heat a cast-iron skillet over high heat for about 3-5 minutes or until super-hot and add the oil. It will shimmer! Place the steak(s) flat (do not overcrowd the pan), lower the heat to medium-high, and cook the steak for 2-3 minutes on each side, or until medium-rare (internal temp: 130 – 135°For 54-57°C).
Transfer the steak(s) to a plate and tent with foil. Let it rest for 3-5 minutes and squeeze the juice of a lime on top. Cut into thin slices against the grain.