Make the fajita seasoning. In a small bowl, whisk together the spice mix and canola oil. Preheat the oven to 400 degrees. Place the chicken on half of the sheet pan and the veggies on the other half. Pour half of the spice mixture on both sides and toss keeping them separate. Bake for 15-20 minutes or until the chicken is cooked thoroughly. Remove the pan from the oven and set aside.
How to assemble and fry quesadillas
Coat a large skillet set over medium flame with butter and warm 2 tortillas on both sides until warmed through. Sprinkle about ¼ cup of cheese on one tortilla followed by ¼ of the chicken and peppers. Top with another ¼ cup of cheese. Flip the second tortilla onto the cheese with the toastiest side up and press down with a spatula. Remove the finished quesadilla to a clean plate and repeat.