Cook the Spaghetti: Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Reserve 1/2 cup of the pasta cooking water, then drain the spaghetti and set aside.

Sauté Sun-Dried Tomatoes and Garlic: In a large skillet, heat the olive oil over medium heat. Add the chopped sun-dried tomatoes, minced garlic, and red pepper flakes (if using). Sauté, stirring frequently, until fragrant, about 2 minutes.

Add Spinach: Add the spinach to the skillet and cook until it wilts, about 1-2 minutes, stirring to incorporate it with the other ingredients.

Make the Creamy Sauce: Pour in the half-and-half and add the Parmesan cheese, stirring until the cheese is melted and the sauce is creamy and slightly thickened, about 2-3 minutes. Season with salt and black pepper to taste.

Combine with Spaghetti: Add the cooked spaghetti to the skillet, tossing to coat it evenly with the sauce. If the sauce is too thick, gradually add a bit of the reserved pasta cooking water until you reach your desired consistency.

Serve: Serve the pasta warm, garnished with extra Parmesan cheese if desired.