Heat oil in a large pot over high heat.
Cook onion until translucent.
Add beef, salt, and pepper, cooking until all the moisture has evaporated and the beef is browned.
Add crushed tomatoes, vodka, and chili flakes, stirring and cooking until half of the liquid has evaporated and the sauce has reduced.
Add cream, stirring until evenly incorporated.
Stir in pasta until evenly coated.
Serve with parsley and Parmesan.