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Debra

Flank Steak Fajitas

Tender, juicy flank steak fajitas made three ways — cast-iron skillet, grill, or sheet pan in the oven. With charred peppers and onions, warm tortillas, and the doneness and slicing tips that make lean flank turn out perfectly every time.
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Prep Time 15 minutes
Cook Time 15 minutes
Total Time 30 minutes
Servings: 6 servings
Course: Dinner, Main Course
Cuisine: Mexican, Tex-Mex
Calories: 340
Ingredients Equipment Method Notes

Ingredients
  

Steak & Veggies
  • 1 1/2 lbs flank steak
  • 3 bell peppers mixed colors, sliced into strips
  • 1 large onion sliced
  • 2 tbsp avocado oil or other high-smoke-point oil
  • 2 1/2 tbsp fajita seasoning homemade or store-bought
  • 1 lime plus wedges to serve
To Serve
  • 8 flour or corn tortillas warmed
  • toppings: guacamole, pico de gallo, sour cream, cheese, cilantro optional

Equipment

  • Cast-Iron Skillet, Grill, or Sheet Pan
  • Instant-read thermometer
  • Cutting Board and Sharp Knife

Method
 

  1. Optional but recommended: marinate the flank steak 2 to 4 hours (don't exceed 4 hours with a citrus marinade). Otherwise, season it well with the fajita seasoning.
  2. Skillet method: Heat a cast-iron skillet until screaming hot. Pat the steak dry, oil it, and sear the whole steak 3 to 5 minutes per side to 130–135°F. Set aside to rest.
  3. Grill method: Build a two-zone fire. Sear over direct heat 4 to 5 minutes per side, moving to the cooler side to finish if needed, to 130–135°F. Rest.
  4. Oven / sheet-pan method: Preheat oven to 425°F with the pan inside. Spread peppers and onions in a single layer (don't crowd) and roast ~15 minutes. Broil the steak 4 to 5 minutes per side to 130–135°F, then finish the veggies under the broiler 2 to 3 minutes for char.
  5. Cook the peppers and onions over high heat until charred and tender-crisp, salting at the end (skillet and grill methods).
  6. Rest the steak 5 to 10 minutes, then slice thinly against the grain (the grain runs lengthwise on flank). Squeeze lime over, combine with the veggies, and serve with warm tortillas and toppings.

Notes

Don't overcook it: flank is lean, so pull it at 130–135°F (medium-rare) and never past 145°F, or it toughens.
Rest, then slice against the grain — on flank the grain runs lengthwise; cut straight across it into thin slices. This is the difference between tender and chewy.
Char, not soggy: don't crowd the peppers (steam makes them soggy), use high heat, and salt at the end.
No time to marinate? Cook the steak, then rest it 10 minutes in a lime-garlic-oil mixture — a reverse marinade.
Leftovers: store sliced with the pan juices; reheat gently, covered, never a hard microwave. Great as fajita bowls, quesadillas, or breakfast hash. Fridge 3–4 days.