Cook the pasta according to the package instructions. Reserve ½ cup of pasta water, then drain and set aside.
In a large skillet over medium heat, heat olive oil. Add the chopped onion and sauté until translucent.
Stir in the garlic, tomato paste, and red pepper flakes. Cook for about 2 minutes until fragrant.
Pour in the vodka and stir, letting it simmer for 1-2 minutes to cook off the alcohol.
Reduce the heat to low and slowly add the heavy cream, stirring until well combined.
Add the cooked pasta to the sauce, stirring to coat. Use reserved pasta water as needed to reach the desired consistency.
Stir in Parmesan cheese, butter, salt, and black pepper.
Serve immediately, garnished with fresh basil and extra Parmesan if desired.