In a Dutch oven or large pot over medium heat, add the butter. Once melted, add the onions and cook until softened, about 3 minutes. Add the garlic and continue cooking for 1 minute.
Add the sun-dried tomatoes and the tomato paste. Cook, stirring constantly, for about 2 minutes.
Stir in broth, cream, basil, salt, Italian seasoning, garlic powder, and crushed red pepper.
Bring to a light boil over medium heat and cook for about 12 minutes.
Add the pasta and reduce heat to medium-low. Cook, stirring occasionally, until pasta is al dente, about 10 minutes.
Reduce heat to low. Add spinach, chicken, cream cheese, and Parmesan. Cook, stirring often, until cream cheese and Parmesan are melted and chicken is heated through, about 5 minutes.
Garnish with additional Parmesan, basil, and red pepper. Serve immediately.