Boil a large pot of salted water.
Cook 8 oz dried short pasta until just before al dente. Reserve 1 cup pasta water, then drain.
In a large skillet, melt 4 tbsp unsalted butter over medium-low heat.
Sauté diced onions for 10 minutes until soft and translucent, adding 2 tbsp water to deglaze the pan.
Cook for an additional 5-10 minutes, seasoning with salt.
Stir in grated garlic and 1 ½ tsp Calabrian chili paste, sauté for 1 minute.
Over medium heat, add ¼ cup tomato paste and cook for 2-3 minutes until it darkens to brick-red and starts to stick to the pan.
Stir in ¼ cup vodka and simmer for 1-2 minutes until the liquid evaporates.
Reduce heat to medium-low, stir in 1 cup heavy cream, and simmer for 5-8 minutes until the sauce thickens and turns bright orange.
Season with salt. Add ¼ cup grated Parmigiano-Reggiano cheese and cooked pasta to the sauce.
Loosen with reserved pasta water as needed, simmer for 1-2 minutes until the sauce clings to the pasta.
Adjust seasoning with salt and pepper.
Divide among bowls, top with basil leaves and additional grated cheese if desired.