Combine 4 cups of cold brew coffee.
Submerge the skirt steak completely into the cold brew mixture, ensuring every inch is soaked.
Add 1 tablespoon of salt.
Place in the refrigerator to marinate while the acidity gently tenderizes the beef for 12 hours.
Remove the steak from the marinade and thoroughly pat it completely dry with paper towels.
Place the steak on a wire rack inside the fridge for another 45 minutes to let the surface dry out completely.
Heat your cast iron skillet and add a generous spoonful of high-quality beef tallow.
Drop the skirt steak straight into the hot tallow over intense high heat, pressing it firmly into the pan to guarantee maximum contact.
Using tongs, flip the steak to sear the opposite side and set that final crust on the backside.
Transfer the steak to a board and let it rest so the juices can settle before slicing.