Add the soy sauce, Worcestershire sauce, garlic, lemon zest, lemon juice, avocado oil, salt, and pepper to a medium-sized bowl and whisk until emulsified. Briefly set it to the side.
Pat the skirt steak dry on all sides using paper towels.
Next, add the steak to a 13x9 casserole dish and cover it in the marinade. Massage the marinade into the steak on all sides.
Cover with plastic wrap and refrigerate for 4 to 24 hours. The longer the marinade time, the more flavorful it will be.
Remove the steak from the fridge and preheat the grill to high heat (500° to 550°).
Take the steak straight from the pan to the grill and cook for 1 minute. Flip it over and cook for another minute. Flip it back over, turn it 45°, and cook for 1 minute. Flip it and cook for 1 additional minute. This will get you to a 125° medium rare internal temperature.
You can sear the steak in oil in a cast-iron or like pan over medium-high heat. You’ll most likely have to cut it in half because it is so long. Sear it for 90 seconds per side and rest it.
Remove the steak and rest on a rack over a sheet tray.
To slice, cut it every 4 to 5 inches. Then turn those slices 45° and make thin slices on a bias against the grain. You do this to cut those long muscle fibers so the steak is tender.
Serve with chimichurri sauce or your favorite sauce.
Notes
Thin cuts of steak, like skirt steak, love high heat. I suggest giving your grill or skillet plenty of time to preheat so you don’t accidentally cook the steak slowly at a low temperature. I want my meat to sizzle throughout the 4-minute cook time, so I always make sure my grill is between 500ºF and 550ºF before I get started.Trim if needed: Before marinating, I’ll trim away any silver skin (the shiny, tough membrane) and any large chunks of hard white fat from the steak. Thin flecks of fat are fine. That’s just pure flavor. Marinating time: You can marinate skirt steak for a minimum of 4 hours or up to 24 hours in the fridge. Remember that the longer it soaks, the more flavorful it will be.Cross-hatch grill marks: After grilling the steak on both sides for 1 minute each, I turn the steak 45 degrees and cook it another minute on both sides. This gives it those classic grill marks and brings it up to medium-rare. Aim for medium-rare: Medium-rare (an internal temperature of 125°F before resting) is the sweet spot for the juiciest skirt steak. If that’s a tad too pink for you, you can leave it on the grill until the internal temperature reaches 135°F for medium.Customize the marinade: The beauty of this marinade is how customizable it is. Sometimes, I’ll add a couple of tablespoons of my Mexican spice blend, some grated ginger, a pinch of red chili flakes, or a spoonful of brown sugar for extra flavor. It always tastes great as long as I follow the basic ratio of 2 parts oil, 1 part acid, and 1 part savory sauce/seasoning.Make-Ahead: I like serving the steak right away, but you can keep it covered in a 200°F oven for up to 30 minutes.How to Store: Store cooled leftovers in an airtight container in the refrigerator for up to 4 days. They also freeze well for up to 3 months. How to Reheat: I add some oil or a splash of broth to a large skillet over medium-high heat. Once it’s hot, I’ll place the steak strips into the pan and sauté until they’re warmed through (about 3 to 5 minutes).