To the same cast iron, add in the olive oil and garlic, and cook for about 1 minute.
Add in the canned tomatoes, dried oregano, dried basil, onion powder, salt, and pepper.
Cover and simmer for 10 minutes. Add in the basil sprigs and simmer for 2 more minutes.
Remove the sprigs of basil and add the chicken back to the pan, spooning some of the sauce over the chicken and top with mozzarella and bake until the chicken is cooked through and the cheese is melted, approximately 8 to 10 minutes. If your chicken is on the thinner side and has already been cooked through, simply remove the pan from the oven once the cheese has melted.
Top with fresh basil before serving if desired.