Pour the oil from the sun-dried tomatoes into a large skillet over medium heat and set the tomatoes aside; slice them if desired.
Season the cubed chicken with 1 teaspoon of the Italian seasoning, salt, paprika, red pepper flakes, and black pepper; toss to coat.
Cook the seasoned chicken in the skillet over medium heat until browned and cooked through, about 6–8 minutes depending on size; sprinkle with 1/4 cup grated Parmesan, then remove the chicken from the pan and set aside.
Add butter to the same skillet, then sauté the diced onion and minced garlic over medium heat until the onion is soft, about 5 minutes.
Stir in the remaining 1 teaspoon Italian seasoning, then add the water, heavy whipping cream, and uncooked pasta to the skillet.
Bring the mixture to a gentle boil over medium-high heat and cook, stirring occasionally, until the pasta is tender and most liquid is absorbed, about 8–12 minutes.
Reduce heat to low and stir in the fresh spinach, cooked chicken, and the reserved sliced sun-dried tomatoes; heat until spinach wilts and everything is warmed through.
Remove from heat and sprinkle with shredded Parmesan cheese before serving.