Preheat oven to 450 degrees. Cut peppers in half and deseed/core. Spray a baking tray and both sides of the peppers with cooking spray.
Season both sides of pepper (with additional salt and pepper to taste) then place in oven, on the cooking tray, for 20-25 minutes, insides facing up (until soft and starting to brown)
Spray a large pan with cooking spray and heat up on the stove over medium heat. Cook garlic and cook for two minutes, until fragrant
Add ground chicken and season with the seasonings. Break up the chicken and stir until completely cooked
Add in the crushed tomatoes and allow them to simmer for 3-5 minutes
Stuff meat mixture into the peppers, evenly top with cheese and pepperoni then bake for another 5 minutes or until cheese is melted