Penne alla Vodka

Ingredients

• pound penne
• garlic, minced
• whole medium onion, chopped finely
• tablespoons butter
• tablespoons olive oil
• vodka
• One 14-ounce can tomato puree or tomato sauce
• heavy cream
• generous pinch red pepper flakes, plus more if needed
• to 1/2 teaspoon salt
• Freshly ground black pepper
• Grated Parmesan, for serving