Heat BBQ and grill the peppers until they are evenly charred and slightly softened. Remove from grill and slice into long strips. Set aside and keep warm.
Juice ½ of the lime and cut the remaining half into wedges for serving, set aside.
In a medium bowl, add the chicken, 1 tablespoon of olive oil, spices, and the lime juice. Combine until the chicken is evenly coated.
Heat 1 tablespoon of olive oil in a large cast iron pan over medium high heat. Once hot add the chicken and sear until both sides are blackened and the chicken is cooked through. Set aside and keep warm.
Wipe out the pan slightly and add the remaining olive oil. Add the sliced onion, season with salt and pepper, and cook over medium heat until softened, about 5-7 minutes.
Return the chicken to the pan, add the peppers, and toss until combined and warmed through. Serve in tortillas with your favorite fajita toppings.