Combine all seasoning ingredients in a small bowl and stir to combine. If using coconut aminos, omit from the spice mix and rub it directly onto the steak. Sprinkle the combined spice mix over the steak and let sit for 30 minutes at room temperature (or refrigerate overnight).
Heat a large cast iron pan over medium-medium high. When hot, add a bit of avocado oil and when the oil is hot, add the skirt steak, pressing to ensure good contact with the pan for the best sear. Cook fro about 3 minutes per side for medium-rare, or until desired doneness. Let the steak rest for 10 minutes before slicing against the grain for the most tender result.