Carne Asada

The sweet spot is 4–8 hours in the fridge. In that window, the citrus acid penetrates the fibres, breaks down connective tissue and loads the meat with flavour. Past 8–10 hours, the acid starts denaturing the surface protein layer: the outside turns soft and slightly mushy, and after grilling the texture is wrong — dry on the outside, oddly soft. Overnight (8–10 hours) is acceptable if the marinade is heavy on orange and light on lime. Never marinate flank or skirt steak for more than 12 hours under any circumstances.

Flank and skirt steak have long, clearly visible muscle fibres running in one direction. Cut along those fibres and each bite is a long, chewy strand. Cut across them — perpendicular to the lines, at a 45° angle — and you're slicing each fibre into short 3–4 mm segments that require almost no chewing. The slices should be thin: no thicker than 4 mm. Do this after the steak has rested for 5 minutes on the board. If the meat still feels tough after correct slicing, the steak was overcooked past medium — flank steak dries out above 65°C (150°F) internal temperature.

A cast iron skillet heated to maximum gets close enough that most people can't tell the difference. The key is temperature: the pan must be visibly smoking before the steak goes in. Don't add oil — the olive oil in the marinade is sufficient and extra oil will smoke excessively. Cook 3–4 minutes per side without touching. You're looking for a dark, almost blackened crust on the surface — not grey steamed meat. A broiler (oven grill) on maximum also works: steak on the top rack, 4–5 minutes per side. Either way, open a window — there will be significant smoke.

Skirt steak (diaphragm muscle, called arrachera in Mexico) is the more traditional cut: fattier, more intensely flavoured, and more forgiving if slightly overcooked. Flank steak is leaner, produces cleaner slices for tacos, and is more widely available outside North America. Both work with the same marinade. If neither is available, a thin-cut chuck steak pounded to 1–1.5 cm thickness is a workable substitute. Avoid thick cuts entirely — carne asada is a fast, high-heat cook and anything over 2 cm won't char outside and stay pink inside simultaneously.

Three components do the work: citrus juice (lime plus orange) tenderises the fibres before the steak hits the heat; olive oil forms a thin coating that slows moisture loss during the fast, high-heat cook; and 1–2 tablespoons of soy sauce add umami depth and speed up caramelisation of the crust. The most important factor after the marinade is not overcooking: a 1.5 cm flank steak reaches medium-rare (57°C) in 6–8 minutes total on screaming-hot metal. At medium (63°C) it's still juicy. Beyond that, flank steak dries out quickly and no marinade can fix it.