Place the chopped spinach in a large colander. Bring a large saucepan of water to a boil, add the whole-wheat spaghetti, and cook according to package directions.
Drain the pasta over the spinach in the colander to wilt the spinach.
Meanwhile, heat the sun-dried tomato oil in a large skillet over medium heat. Add the onion and sun-dried tomatoes, and cook until softened, about 3 minutes.
Stir in the garlic, crushed red pepper, salt, and pepper, and cook for an additional 1 minute.
Increase the heat to medium-high, add the broth, and cook until reduced by half, about 2 minutes.
Stir in the sour cream, Parmesan cheese, and butter until well combined.
Add the cooked spaghetti and wilted spinach to the skillet, tossing to coat evenly with the sauce.