Begin by combining fajita seasoning, olive oil, lime juice, and Worcestershire sauce in a mixing bowl. Reserve a small amount of this mixture for the vegetables later. Place your skirt steak into a sealable bag, pour in the marinade, and seal it tightly. Gently massage the bag to evenly coat the steak. Marinate in the fridge for at least 30 minutes, though overnight is ideal for deeper flavor.

Slice your onion and bell peppers into even strips. Toss them together with the reserved marinade in a separate bowl. This step ensures the veggies soak up the bold fajita seasoning, complementing the steak perfectly.

Preheat your cast iron skillet over medium-high heat. Once it’s hot, place the marinated steak into the skillet. Sear each side for 3-4 minutes to develop a deep, golden char. Use an instant-read thermometer to ensure the internal temperature reaches around 130°F for medium-rare. Set the cooked steak aside to rest for 10 minutes to lock in the juices.

After removing the steak, add the marinated veggies to the same skillet. Cook for 5-7 minutes, stirring occasionally, until they become tender and slightly caramelized.

Thinly slice the skirt steak against the grain (explained in more detail below). Return the slices to the skillet with the vegetables to keep them warm. Warm your tortillas in a clean pan or over an open flame, then assemble the fajitas with steak, veggies, and your favorite toppings.