In a medium sized bowl, whisk together orange juice, garlic, 1 cup of the cilantro, cumin, jalapeño (optional), cayenne or achiote, salt, and pepper.
Place skirt steak in shallow pan or bowl.
Pour marinade over skirt steak.
Marinade one side for 1 hour. Flip steak and marinade the other side for 1 hour.
After marinating, preheat cast iron skillet on stovetop until smoking hot. Add avocado oil.
Place marinated skirt steak (without the marinade) in smoking hot skillet. Depending on thickness of steak and your preference for how well done you like your steak, sear each side for 3 - 5 minutes. If you like steak well done, cook up to 7 minutes.
TIP: Turn steak in pan only once. Your steak will toughen the more you flip it.
Remove from skillet onto a cutting board. Using foil, tent the cooked skirt steak and let rest for 5 - 10 minutes.
After resting, slice skirt steak against the grain using a sharp knife.
Serve with grilled spring onion, freshly made corn tortillas (GF), fresh cilantro, chopped cabbage, and sour cream.