Zest the limes with a microplane grater or fine grater. Once the zest is grated, place it on a paper towel lined plate to dry out for 2-3 hours
While the lime zest is drying, lightly toast the chiles de arbol in a dry pan. Set aside.
In a spice grinder or Vitamix, add the chiles de arbol and grind until you get a medium/medium-fine powder. Next, add the lime zest and grind until you have a medium-fine powder.
Mix the chile/lime zest powder with salt in a small bowl.
Remove the skirt steak from the fridge for 30 minutes to take the chill off.
Preheat a grill to medium-high heat.
Once the grill is hot, season the skirt steak with chile/lime salt.
Place the skirt steak on the grill and cook for 2 minutes on one side. Then flip the skirt steak and cook for another 2 minutes. Depending on the thickness you may need to cook it for a little longer.
Once the skirt steak is done, allow it to rest for at least 10 minutes before slicing. When slicing, make sure to slice it against the grain.