01 - Preheat oven to 400°F. Lightly grease a baking dish with cooking spray or olive oil.
02 - In a large bowl, toss the sliced bell peppers and red onion with olive oil, chili powder, smoked paprika, ground cumin, garlic powder, onion powder, salt, and black pepper until evenly coated.
03 - Butterfly each chicken breast by slicing horizontally through the middle without cutting all the way through. Place each butterflied breast between sheets of plastic wrap and pound to an even 1/4-inch thickness using a meat mallet or rolling pin.
04 - Divide the seasoned vegetable mixture and shredded Monterey Jack cheese evenly among the flattened chicken cutlets. Lay the filling across the center of each piece.
05 - Roll each chicken breast tightly around the filling, tucking in the edges. Secure with toothpicks to hold the seam closed during baking.
06 - Place the roll ups seam-side down in the prepared baking dish. Sprinkle any remaining fajita seasoning blend over the top of each roll up.
07 - Bake for 25 to 30 minutes, or until the internal temperature of the chicken reaches 165°F and the cheese is melted and bubbling.
08 - Remove the toothpicks from each roll up. Garnish with chopped fresh cilantro and serve alongside lime wedges and sour cream if desired.