Position an oven rack about 4 inches (10cm) below the upper heating element and preheat your broiler on high (or turn on the grill setting).
Whisk the Fajita seasoning with lime zest and olive oil in a large baking pan.
Cut the chicken into 1-inch (2.5 cm) thick strips. Cut the peppers into 1/4-inch (5mm) thin strips, cut onion in half, and slice slightly thicker than bell peppers.
Add the chicken, bell pepper, and onions to the baking sheet. Toss until evenly coated in the seasoning. Season with salt and pepper. Spread in an even layer on the sheet pan.
Broil for about 10-15 minutes or until the chicken is cooked through and browned. Keep an eye on the chicken to prevent it from burning.
Take the baking sheet out of the oven and drizzle the chicken with lime juice.
Sprinkle with shredded cheese. Bake again for 1-2 minutes or until the cheese is melted.
Enjoy!