Prepare the steak:
Pat the skirt steak dry with paper towels.
In a small bowl, mix garlic powder, smoked paprika, cumin, salt, and pepper. Rub this spice blend evenly over both sides of the steak.
Drizzle olive oil over the steak to help the seasoning adhere.
Make the avocado chimichurri:
In a mixing bowl, mash the avocado until smooth.
Stir in parsley, cilantro, garlic, red wine vinegar, lime juice, olive oil, crushed red pepper flakes (if using), salt, and pepper. Mix until well combined. For a smoother sauce, blend the ingredients in a food processor or blender.
Cook the steak:
Preheat your grill or grill pan to high heat.
Place the steak on the hot grill and cook for 3-4 minutes per side for medium-rare, or longer for your preferred doneness.
Remove the steak from the grill and let it rest for 5-7 minutes to allow the juices to redistribute.
Slice and serve:
Slice the skirt steak against the grain into thin strips.
Spoon the avocado chimichurri generously over the steak.