Melt the butter in a large, heavy-bottomed pot over medium heat
Add the onions and cook for 18 to 20 minutes, stirring often, until golden brown and caramelized
Cook the garlic and chiles for two minutes, or until fragrant
About 2 teaspoons of the cooked onion mixture should be placed in a small bowl and left there
Add the tomato paste to the pot and cook for 2 to 3 minutes, stirring often, until slightly thickened and deeper in color
Add the tomatoes, their liquid, and the vodka, scraping off any browned bits from the pot's bottom
Bring to a simmer
Cook for about ten minutes, breaking up the tomatoes, until the sauce thickens
Remove from the heat and stir in the heavy cream until thoroughly mixed
Use an immersion blender or a normal blender to smooth up the sauce
Put the sauce back into the pot
In a large saucepan of boiling water, combine pasta and 2 tablespoons salt. Cook according to package directions until al dente
Before draining, reserve 1 1⁄2 cups of pasta water
Return the sauce to medium-low heat to simmer
Mix in Parmesan and ½ cup pasta water until mixed
Add salt to taste
Toss the pasta in the sauce with the reserved cooked onion mixture until well heated and coated
Serve immediately and top with a little Parmesan cheese
