Cook the pasta according to package instructions. Drain in a colander and rinse it under cold water to stop it from cooking any further. Reserve some of the pasta water, just in case we need it to thin out the sauce. Heat the olive oil in a large skillet over medium-high heat. Add the onion and cook for 3 to 5 minutes until it softens and becomes translucent. Add the garlic and cook for another 30 seconds until it becomes aromatic. Add the vodka, stir and cook for a couple minutes until the almost all of the vodka has cooked down. Stir in the nutmeg, red pepper flakes, salt and pepper. Add the tomato puree to the skillet, then stir in the half and half or heavy cream. Bring to a boil. Stir in the cooked pasta, bacon and the Parmesan cheese. If the sauce is too thick and the pasta has soaked up all the sauce, add some of the reserved pasta water. Garnish with parsley and serve.