1. Bring a large pot of salted water to a boil and cook the rigatoni pasta until al dente according to package instructions. Reserve 1 cup of pasta water before draining.

2. Heat olive oil in a large deep skillet over medium-high heat. Add the Italian sausage and cook until browned and fully cooked, breaking it apart with a spoon as it cooks. Remove sausage and set aside.

3. In the same skillet, add diced onion and cook for 3 to 4 minutes until softened. Stir in minced garlic and cook for 30 seconds until fragrant.

4. Pour in the chicken broth and scrape the bottom of the skillet to release flavorful browned bits. Simmer for 2 minutes.

5. Reduce heat to medium-low and stir in the heavy cream, Italian seasoning, black pepper, crushed red pepper flakes, and salt. Simmer gently for 3 to 5 minutes.

6. Gradually add the parmesan cheese while stirring continuously until melted and smooth.

7. Stir in the chopped sun-dried tomatoes and fresh spinach. Cook until the spinach wilts.

8. Return the cooked sausage to the skillet and stir well to combine with the sauce.

9. Add the cooked rigatoni pasta and toss until fully coated in the creamy sauce. Add reserved pasta water if needed to loosen the sauce.

10. Remove from heat, let rest for 2 minutes, then garnish with chopped parsley and extra parmesan before serving.