Bring a large pot of salted water to a boil and cook the pasta until al dente. Reserve 1/2 cup of pasta water before draining.
Heat the olive oil in a large skillet over medium heat, then add the onion and garlic. Sauté 4-5 minutes, stirring frequently until the onions are soft and translucent and the garlic is fragrant.
Next, stir in the tomato paste until it completely coats the onion and garlic. Continue to cook, stirring often, until the paste is deep red and starting to brown on the bottom of the pan, about 5 minutes.
Next, pour in the vodka, and continue stirring to incorporate, scraping up any browned bits from the bottom of the pan, cook 3-4 minutes. Reduce the heat to low then whisk in the heavy cream and reserved pasta water followed by the parmesan cheese.
Turn off heat and gently fold in the cooked pasta, butter, and crushed red pepper (optional). Season with salt if needed. Serve with fresh basil and extra parmesan cheese!
To Freeze: Vodka sauce can be made, then frozen in a freezer-safe container for up to 3 months. Thaw, then use as directed.