Boil the pasta according to package directions. Reserve ½ cup of pasta water. Drain and set aside.
Heat the oil in a large skillet over medium heat. Add the onions and garlic and cook for about 5 minutes until softened.
Stir in the tomato paste and cook for 1 minute.
Add the vodka and boil for 1-2 minutes until evaporated.
Add the heavy cream, salt, black pepper, and red pepper flakes. Bring to a simmer and let it bubble for a few minutes until thickened.
Stir in the cooked pasta and serve with grated parmesan cheese on top. If the pasta is too thick, stir in a little bit of the reserved pasta water. Enjoy!
Nutrition information is calculated using an ingredient database and should be considered an estimate.