A skirt steak taco should be a simple thing, so why do so many places get it wrong? Much of the trouble comes down to the cooking method. Too many taquerias let the beef cook forever on a griddle, only checking on it to chop up the bits with a spatula. Skirt steak deserves better.
Sure, it loves high heat, but the steak also needs to be coddled, or it will pay back your carelessness by being tough and chewy. Basically, it needs to be treated like the steak it is. Cook it to medium-rare, let it rest, and then cut it against the grain into thin slices.
As Kenji found out, a fierce charcoal fire is probably the best option, but without the abilities to set one up in the winter, I settled for the next best thing: my oven's broiler. Setting the rack to the highest position, I was able to get a great char on the beef, while nailing the desired medium-rare.
With the broiler ready to go, I couldn't help but add some rajas, or poblano strips. Much spicier than bell peppers, with a distinct smoky profile from the flame, they go exceptionally well with beef. Just char them under the broiler, steam in a bag for ten minutes, and their blackened skins fall right off. Now they are ready to be stemmed, seeded, and cut into thin strips.
An assertive tomatillo salsa would do well here, but I wanted something creamy to counter the crisp and assertive ingredients. Only guacamole would do. This is not the time for a bland dip; make a spicy version and don't be skimpy with the lime juice.
Tasting sort of like mini-burritos with all the extraneous ingredients expelled, two of these skirt steak tacos make for a solid meal, though some pinto beans would also help round this meal out.