Mix all the ingredients in a blender until well combined.
Pour the marinade over the skirt steak and rub it in.
Cover and refrigerate for 2-4 hours, or overnight for best results.
Prepare a hot grill and clean the grates with a halved onion.
Grill the marinated steak, flipping frequently, until it reaches your desired doneness.
Slice the grilled steak and serve on warm tortillas with your favorite toppings and salsas.
