Season the boneless, skinless chicken breasts with salt and black pepper. Heat olive oil in a large skillet over medium heat. Sauté the chicken for about 6-8 minutes until golden brown and cooked through. Remove the chicken from the skillet and set it aside to cool.

In the same skillet, add more olive oil if necessary, and toss in the chopped onion. Sauté for about 5 minutes until soft and translucent. Add in minced garlic and cook for another minute until fragrant.

Stir in a can of crushed tomatoes and a can of tomato sauce into the skillet. Add dried oregano, basil, and optional red pepper flakes. Mix well and let it simmer for 15 minutes over low heat, stirring occasionally.

Return the cooked chicken to the skillet, mixing it into the sauce and letting everything combine for an additional 5 minutes.

While the sauce is simmering, bring a large pot of salted water to a boil and add the pasta. Cook according to package instructions until al dente, about 8-10 minutes. Drain the pasta in a colander without rinsing it.

Preheat your oven to 375°F (190°C).

In a large mixing bowl, combine the drained pasta with the sauce and chicken mixture, stirring gently until the pasta is coated with sauce.

Pour the pasta mixture into a greased 9x13 inch baking dish, spreading it out evenly.

Sprinkle shredded mozzarella, cheddar, and Parmesan cheese over the pasta in an even layer.

Place the baking dish in the preheated oven and bake for 20-25 minutes until the cheese is melted and bubbly.

Let the Cheesy Chicken Pasta Bake rest for about 10 minutes before serving. Garnish with chopped fresh parsley if desired.