Add the cilantro, parsley, garlic, salt, cumin, and red pepper flakes to a food processor. Pulse until the leaves are coarsely chopped, about 5 pulses.

Add the red wine vinegar, pulse 5 times. Add the olive oil, pulse 5 times. The chimichurri sauce should be emulsified and the herbs coarsely chopped.

Transfer the chimichurri sauce to a medium bowl. Cut the avocado into ½-inch dice. Add the avocado to the chimichurri and gently stir to combine. Cover and refrigerate until ready to use.

If the skirt steak comes in a long strip, cut across the grain into 2 to 3 smaller pieces, about 5 to 7 inches in length.

Thoroughly pat dry each steak with paper towels on each side. Generously season each side of the steaks with salt and pepper.

Heat a large 12-inch cast-iron skillet over high heat for 3 minutes. Once hot, add the olive oil.

Use tongs to carefully add the steak to the pan, then press down on the surface a few times for more contact. Sear the first side until browned, about 2 to 4 minutes depending on the thickness of the meat. Flip and cook another 2 to 4 minutes.

For medium-rare doneness, cook steak until it reaches an internal temperature of 130°F.

Transfer steak to a cutting board, loosely cover with foil and rest for 10 minutes before slicing.

Hold the carving knife at a 45-degree angle and then slice the steak against the grain, about ¼-inch thick slices. Transfer skirt steak to a serving plate and either top with avocado chimichurri sauce or put the sauce on the side.