01 - Preheat oven to 400°F. Lightly grease a large baking dish with 1 tablespoon of olive oil, coating the bottom and sides evenly.
02 - Arrange the sliced red, yellow, and green bell peppers along with the thinly sliced red onion in an even layer across the bottom of the prepared baking dish. Drizzle with the remaining olive oil and sprinkle with half of the salt, black pepper, Italian seasoning, and smoked paprika. Toss the vegetables gently to coat evenly.
03 - Pat the chicken breasts dry with paper towels. Season both sides of each breast with the remaining salt, black pepper, Italian seasoning, and smoked paprika, pressing the spices gently into the meat.
04 - Place the seasoned chicken breasts on top of the bed of vegetables in the baking dish. Scatter the minced garlic evenly over the chicken and peppers.
05 - Cover the baking dish tightly with aluminum foil and bake for 20 minutes, allowing the chicken to cook through gently while the vegetables soften and release their juices.
06 - Remove the foil and sprinkle the shredded mozzarella and grated Parmesan cheeses evenly over each chicken breast. Return the dish to the oven uncovered and bake for an additional 10 minutes, or until the chicken reaches an internal temperature of 165°F and the cheese is fully melted with a golden, bubbling top.
07 - Remove the dish from the oven and let the chicken rest for 5 minutes before serving. This allows the juices to redistribute, ensuring moist and tender results. Serve directly over the roasted peppers and onions.