Put the 6 halved mini sweet peppers (12 pieces) on a broiler-safe dish or cooking tray. Set aside.
Spray a frying pan with cooking spray. Saute sliced onion and 3 sliced peppers over medium heat until softened and golden.
Preheat the broiler.
Add the chicken, cream cheese, and fajita seasoning to the frying pan and stir until the cream cheese is melted and the chicken is warm. Put the chicken, onion, pepper mixture on top of the halved peppers. Top with the cheese. Broil for 2-3 minutes or until the cheese is melted and bubbly. Do not walk away from the oven. Watch the cheese through the window. It is very easy to burn food while broiling. (Trust me, I know from personal experience).
Remove the plate from the oven and top with your favorite topping. I put sour cream, chunks of avocado, and cilantro on mine. Grab a pepper, scoop up some toppings, and ENJOY!