Boil: Cook rigatoni according to package directions; drain and set aside.
Season Chicken: Massage olive oil over chicken. Season with paprika, onion powder, garlic powder, Italian seasoning, salt, and pepper.
Sear: In a large skillet over medium-high heat, cook chicken for 5–7 minutes per side (internal temp 165°F). Remove and chop into bite-sized pieces.
Sauté: Lower heat to low. Add butter, onions, and tomato paste to the same skillet. Stir and cook for 2–3 minutes.
Roux: Sprinkle in flour, mix well, and cook for another 2–3 minutes to remove the raw flour taste.
Simmer: Whisk in chicken broth, heavy cream, sun-dried tomatoes, and red pepper flakes. Bring to a simmer until thickened.
Finish Sauce: Stir in parmesan and spinach until the cheese melts and spinach wilts.
Combine: Toss the cooked pasta and chicken into the skillet. Mix thoroughly until coated. Serve warm.