In a small bowl, whisk together chili powder, cumin, paprika, sugar, garlic powder, onion powder, cayenne pepper, and salt to taste (I like 1 teaspoon).
To a large zipper-top plastic bag, add chicken, cilantro, lime juice, and fajita seasoning. Mash until chicken is evenly coated. Marinate at least 30 minutes (room temperature) or up to 1 hour (refrigerated).
In a large skillet over medium-high heat, heat oil until shimmering. Add chicken and cook until crispy and browned on one side, about 8 minutes.
Flip and cook until browned on the second side and chicken registers 165 degrees, about 8 to 10 minutes longer. Transfer chicken to a cutting board and rest for 5 minutes before cutting into strips (do not discard fat in skillet).
To the skillet with the fat over medium-high heat, add bell peppers and onions and cook until tender, about 5 minutes. Push peppers and onions to one side and add sliced chicken back to skillet for serving. Serve with tortillas and your favorite toppings.
Fajita seasoning:This recipe uses my favorite homemade blend. For this recipe, I've portioned out exactly what you need to make this recipe if you don't already have a jar on hand.
Chicken: For the juiciest chicken fajitas, use boneless, skinless chicken thighs. After they’re finished cooking, I let the meat rest for 5 minutes, then I slice them up. Substitute chicken breasts if desired.
Yield: Although you start with 2 pounds of raw chicken, you’ll have closer to 1 or 1 1/2 pounds of cooked chicken after cooking. This recipe will make at least 4 servings (1 cup EACH chicken and vegetables per serving).
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: Make the seasoning well in advance and marinade the chicken up to 1 hour before you want to start cooking.