01 - Preheat oven to 400°F. Lightly grease a 9x13-inch baking dish with cooking spray or olive oil.
02 - In a large mixing bowl, combine the sliced bell peppers and red onion. Drizzle with olive oil, then add chili powder, smoked paprika, ground cumin, garlic powder, onion powder, salt, and black pepper. Toss until the vegetables are evenly coated with the seasoning mixture.
03 - Slice each chicken breast horizontally through the center without cutting all the way through, creating a butterfly cut. Open the breast flat, place it between sheets of plastic wrap, and use a meat mallet or rolling pin to pound it to an even 1/4-inch thickness.
04 - Divide the seasoned vegetable mixture and shredded Monterey Jack cheese evenly among the four flattened chicken cutlets. Lay the filling across the center of each piece, then roll each one up tightly. Secure the seams with toothpicks to hold their shape during baking.
05 - Place the rolled chicken seam-side down in the prepared baking dish. Sprinkle any remaining fajita seasoning over the tops of the roll ups for added flavor.
06 - Bake for 25 to 30 minutes, or until the internal temperature of the chicken reaches 165°F and the cheese is melted and bubbly on the edges.
07 - Remove from the oven and carefully extract the toothpicks from each roll up. Let rest for 3 to 5 minutes. Garnish with chopped fresh cilantro and serve alongside lime wedges and sour cream.