In a small bowl, combine fajita spices then add to the chicken and bell peppers. Toss well to combine.
Heat a large ovenproof skillet with oil on medium heat. Add chicken breasts on one side of the skillet and bell peppers on the other side. Sear chicken for a bit more than 1 minute on each side. Place in the oven and bake for 25 minutes.
Remove and sprinkle cheese on top. Bake until the cheese melts. About 10 minutes.
Remove. Allow to rest for 1 minute before serving. Garnish with chopped cilantro.