Pasta a la tequila

Name: Pasta a la tequila
Yield: 2
Ingredients: 3 tablespoons (45g) unsalted butter; 1 medium (8-ounce; 225g) yellow onion, diced; 3 medium cloves garlic, thinly sliced; Pinch red pepper flakes; Kosher salt; One 4 1/2-ounce (130g) tube concentrated tomato paste or 6-ounce (170g) can tomato paste; One 14 1/2-ounce (411g) can whole peeled tomatoes; 1 cup (240ml) heavy cream; 1 pound (450g) short tubular pasta, such as rigatoni or penne; 1/4 cup (60ml) vodka, plus more if desired; 2 ounces (55g) grated Parmigiano-Reggiano, plus more for serving