01 - Preheat oven to 400°F. Lightly coat a 9x13-inch baking dish with 1 tablespoon of the olive oil, ensuring even coverage across the bottom and sides.
02 - Arrange the sliced red, yellow, and green bell peppers along with the red onion in an even layer across the bottom of the prepared baking dish. Drizzle with the remaining 1 tablespoon of olive oil, then sprinkle with half the kosher 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 kosher salt, black pepper, Italian seasoning, and smoked paprika, pressing the seasonings gently into the meat.
04 - Place the seasoned chicken breasts on top of the vegetable bed in the baking dish. Scatter the minced garlic evenly over the chicken and vegetables.
05 - Cover the baking dish tightly with aluminum foil and bake for 20 minutes, allowing the chicken to cook in the steam alongside the vegetables.
06 - Remove the foil and sprinkle the shredded mozzarella and grated Parmesan evenly over each chicken breast. Return the dish to the oven uncovered and bake for an additional 10 minutes, or until the chicken registers 165°F internally and the cheese is melted, bubbly, and golden brown.
07 - Remove the dish from the oven and let the chicken rest for 5 minutes before serving. This allows the juices to redistribute for a more tender result. Spoon the roasted vegetables and pan juices over each breast when plating.