Bring a large pot of salted water to a boil. Add pasta and cook until al dente. Then drain and set aside.
Heat oil in a large pan, on medium high heat, sauté onion, garlic, and butter.
Add tomato paste and cook for a few minutes. Gradually add in pasta water and simmer until thickened.
Add in the heavy cream and simmer until bubbles. Once it starts to bubble, mix in the Parmesan cheese. Taste for salt and pepper.
