Gather all your ingredients and prep: slice the chicken thinly, julienne the peppers and onions, and squeeze fresh lime juice. Keep everything within easy reach for quick cooking.
Heat your cast-iron skillet over medium-high heat until it’s hot and shimmering, with a slight shimmer in the oil when added.
Add a tablespoon of oil to the pan and swirl to coat. Once it shimmers and begins to smoke slightly, add the sliced chicken in a single layer.
Sear the chicken undisturbed for about 3-4 minutes until it develops a golden crust, then flip and cook for another 3-4 minutes until cooked through and no longer pink inside. Transfer the cooked chicken to a plate and cover loosely with foil.
In the same skillet, add another splash of oil if needed, then add the peppers and onions in an even layer. Let them sit undisturbed for about 4-5 minutes until dark spots and some char develop, releasing a smoky aroma.
Stir the peppers and onions, then spread them out again. Repeat this process, letting them sit undisturbed, until they are deeply browned and caramelized, about 8 minutes total.
Slice the rested chicken into thin strips, then return it to the skillet with the caramelized peppers and onions. Toss everything together and cook for another 1-2 minutes to reheat and meld flavors.
Squeeze fresh lime juice over the skillet contents, then give everything a good toss. Taste and adjust seasoning if needed—add a pinch of salt or more lime for brightness.
Remove the skillet from heat. Warm the tortillas in a dry skillet or microwave wrapped in a towel. Serve the smoky chicken and vegetables with tortillas, garnished with cilantro if desired.
Enjoy your flavorful, caramelized pepper and chicken fajitas, straight from the skillet, with plenty of smoky, sweet, and savory layers in every bite.
