Hot and fast, then slice thin across the grain

Don’t overcook it, and slice it right.

Flank steak is lean muscle. It gets tough because people cook it to medium-well and slice it the wrong way. Treat it like a steak, not a roast. You want high heat, short time, and a decent rest.

Marinate if you want — lime, oil, garlic, cumin for an hour — but it’s not required. Pat it dry, salt generously, and throw it on the hottest part of your grill. 4-5 minutes per side for medium-rare. Pull it off at 130°F internal. Let it rest for a full 5-10 minutes. That rest lets the juices redistribute. Skip it and you’ll lose moisture the second you cut.

Then the real trick: slice it very thin, against the grain, on a bias. The grain runs lengthwise. Cut perpendicular to those lines. If you slice with the grain, you’re basically making beef straws that won’t break down in your mouth.

Tough flank steak is almost always a slicing mistake.

Fajitas are about texture, not toughness.