Prep the oven and pan: Preheat the oven to 400°F (200°C).
Lightly grease a 9x13-inch baking dish with olive oil.
Flatten the chicken: Place each chicken breast between two pieces of parchment and pound to an even 1/2–3/4-inch thickness. This helps it cook evenly and stay juicy.
Season well: In a small bowl, mix garlic powder, onion powder, Italian seasoning, smoked paprika, salt, and pepper. Drizzle the chicken with olive oil and rub the seasoning mix all over both sides.
Par-bake the chicken: Arrange the breasts in the baking dish, not overlapping.
Bake for 12–15 minutes, until the centers are just starting to turn opaque. This step ensures the chicken isn’t overcooked later.
Add the “pizza” layers: Remove the dish from the oven. Spoon marinara over each piece (about 1/4 cup per breast).
Sprinkle evenly with mozzarella and Parmesan. Top with pepperoni, olives, and red onion if using.
Finish baking: Return to the oven for 8–12 minutes, until the cheese is melted and bubbling and the chicken reaches an internal temperature of 165°F (74°C).
Broil for color (optional): Switch to broil for 1–2 minutes to brown the cheese slightly. Watch closely to avoid burning.
Rest and serve: Let the bake rest for 5 minutes.
Garnish with chopped basil or parsley. Serve hot with a simple green salad or roasted veggies.