In a large skillet, heat olive oil over medium heat. Add the chopped onion, carrot, and celery, and sauté for about 5 minutes until softened.

Add the minced garlic and cook for an additional minute until fragrant.

Stir in the pumpkin puree, crushed tomatoes, vegetable broth, oregano, basil, salt, and pepper. Bring to a simmer.

Reduce heat and let the sauce simmer for 30 minutes, stirring occasionally.

While the sauce is simmering, bring a pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente.

Drain the pasta and set aside.

Once the sauce has thickened, combine it with the cooked spaghetti in the skillet. Toss to coat the pasta evenly with the sauce.

Serve hot, topped with grated parmesan cheese if desired.