Prepare the veggies on a separate plate so they are ready when you need them.
MAKE THE STEAK FAJITA MARINADE:
In a large shallow dish (or ziplock bag) mix all the marinade ingredients.
Reserve 2 tablespoons for the vegetables later in the recipe.
MARINATE STEAK:
Coat the steak with the marinade and allow it to marinate for 30 minutes or for up to 2 hours in the refrigerator.
Bring the steak to room temperature for 20 minutes before cooking.
PREHEAT SKILLET:
Heat a cast-iron skillet or grill pan over medium-high heat with 1 tablespoon of vegetable oil.
COOK FAJITAS:
Sear the steak for 4 minutes on both sides to achieve medium-rare temperature and 1 minute on both of its sides/edges using kitchen thongs to hold the steak.*** See the notes below for internal temperatures for the steak and desired doneness.
Transfer the steak to a cutting board, sprinkle with sea salt and let it rest while you cook the vegetables.
Wipe the skillet and add the remaining 1 tablespoon of vegetable oil.
Cook the veggies on medium-high heat along with the reserved 2 tablespoons of marinade.
Cook the vegetables until just softened.
Remove the skillet from the heat and season with salt and pepper.
TO FINISH:
Cut the steak into at least ½ inch strips. Add them to the skillet with the vegetables.
Serve with tortillas, avocado, shredded cheese, cilantro, and lime wedges.
Notes
Depending on how you like your steak, the cooking temperatures generally are:
Medium rare: 145 Fahrenheit (soft and pink center)
Medium: 160 Fahrenheit (soft but with less pink or lighter pink in the center)
Well done: 170 Fahrenheit (chewy, firm, and no pink center)