Boil a large pot of salted water and cook your pasta al dente according to the package directions.
In a skillet over medium heat, add the olive oil and butter. Once melted, add the finely chopped onion. Sauté for 5-7 minutes or until softened and lightly browned.
Stir in the minced garlic, then add the tomato paste. Let it simmer for about 30 seconds.
Stir in the vegetable broth, dried oregano and heavy cream until the sauce becomes smooth. Let the sauce simmer for about 5 minutes or until it thickens slightly.
Remove the skillet from the heat and stir in the grated parmesan cheese.
If the sauce has thickened too much, you can thin it with a little hot pasta water. Drain the pasta and add it to the skillet, tossing to coat. Season with salt and pepper as needed.