In a large glass baking dish whisk together Carne Asada marinade ingredients (jalapeño through black pepper) until combined. Add skirt steak in a single layer, turning to coat with marinade. Cover and refrigerate for at least 1 hour, but no longer than 8 hours (longer will begin to break down the meat).
Grill Pan Instructions
Add cast iron grill pan to cold oven and preheat oven to 425˚F.
With oven mitts, remove preheated grill pan from oven and brush lightly with vegetable oil. Arrange steaks in a single layer on grill pan (they should sizzle when they touch the pan). Place in oven and cook 8 to 14 minutes (depending on steak thickness), flipping steaks half way through cooking time for medium-rare (remove from oven when internal temperature reads 130°F).
Line a baking sheet with foil.
Adjust oven rack so that your steak will be about 2 to 3 inches from the heat. Set the oven to broil on high.
Place marinated steak on prepared baking sheet and broil 5 to 7 minutes per side, depending on your desired doneness. (130˚F for medium-rare, 140˚F for medium, 160˚F for well done).
Transfer steak to cutting board and allow to rest for 5 minutes. Slice thinly across the grain and serve.
Ask your butcher or grocery meat counter for 'outside skirt steak' for the most flavorful and juicy results.
Note that the longer you marinate the skirt steak, the more tender and flavorful it will become. But be sure to cook it within 8 hours to maintain the texture of the meat.
For the juiciest steak, I recommend cooking to medium-rare. If you prefer to cook it longer, here are your target internal temperatures before resting the meat: 140˚F for medium, 160˚F for well done.