Arrange oven shelf to the middle of the oven. Preheat broiler (or grill in Australia) on medium heat.

Season chicken with 2 teaspoons of Italian seasoning, paprika, onion powder, salt and pepper.

Heat oil in a pan or skillet over medium heat. Cook chicken on both sides until browned and cooked through (about 8 minutes each side). Transfer to a plate; set aside.

Cook the onion in the same pan until transparent (about 3-4 minutes) scraping any browned bits form the bottom of the pan, then add in the garlic and cook until fragrant (about 1 minute). Add the fire roasted pepper (or capsicum), crushed tomatoes, tomato paste, crushed red pepper flakes (if including) and remaining Italian seasoning. Give it a good stir to mix well.

Bring to a simmer and allow the sauce to thicken while stirring occasionally (about 4 minutes).

Arrange the chicken in the sauce and top each breast with 2-3 tablespoons of mozzarella cheese per breast. Transfer to the oven to broil for 1-2 minutes, or until the cheese in browned and bubbling.