Slice flank steak into strips and place into a freezer bag or storage container with olive oil, lemon, and fajita rub seasonings. Let sit for at least 30 minutes.
Slice bell peppers and onion into strips. Set aside.
Heat a cast iron or heavy bottom skillet to medium high heat. Add oil and the seasoned meat in a single layer. You may have to work in batches so you don’t overcrowd the pan. Sear all the meat for about 1 minute on each side (the small strips will cook quickly). Remove from the pan and set aside.
Next add the veggies to the same pan and sauté for about 5 minutes until slightly softened and tender. Once cooked add the meat back to the pan and turn off the heat.
Serve fajitas in your favorite tortillas with toppings of choice!
