Combine all seasoning ingredients in a bowl and mix together.
Generously sprinkle the steak all over on both sides with the coffee spice rub and gently massage it in. Let steak stand at room temperature for 30 minutes.
Meanwhile, prepare a grill for direct cooking over high heat.
Cook steak directly over the flame, flipping halfway through cooking, until well browned. This is about 3 minutes per side to cook a thin skirt steak medium-rare. Adjust cooking time accordingly depending on the thickness of your steak and desired doneness.
Transfer steak to a carving board and let rest for at least 5 minutes. Slice the steak across the grain and serve.
Nutrition facts are an estimate provided for those following a Ketogenic or low-carb diet. See our full nutrition information disclosure here.