Add the oil, lime juice, garlic, cumin, chili powder, paprika and cilantro to a small bowl and whisk to combine. Place the steak into a large bowl or large Ziploc bag and pour the marinade over the steak. If using a Ziploc bag, massage the bag to ensure the marinade covers the entire surface of the steak. If using a bowl, toss the steak to evenly coat.
Cover and marinate in the refrigerator for a minimum of 2 hours, if time permits.
Right before cooking, remove the steak and transfer to a large cutting board. Pat dry with paper towels. Season liberally with the salt and pepper.
Add 1 tablespoon of oil to a large cast iron skillet and heat over medium-high heat. Add the steak to the skillet and cook for 5.5-7.5 minutes per side, flipping halfway through. (*Note 3) Reference the cooking temp chart in the post if you're unsure of the final temp you're aiming for.
Use a meat thermometer to check the temperature. Remove the steak when it's 5 degrees under what your desired final temp is. Place the steak on a large cutting board and tent with foil. Let rest for 7-8 minutes before slicing.
While the steak is resting, add 1 tablespoons of oil to the skillet and swirl to coat. Add the onions, peppers and salt, to taste. Cook, stirring occasionally, for approx. 6-7 minutes, until the vegetables are soft.
Remove the foil from steak and slice against the grain into thin strips. Serve alongside the cooked vegetables and any other toppings you prefer. Enjoy immediately!