Preheat oven to 375 degrees. Heat the oil in the oven proof skillet under medium heat. Sautee the onion and garlic for a few minutes, then add oregano, hot pepper flakes and a good dash of salt and pepper. Continue cooking, stirring until wilted and fragrant. Add crushed tomatoes and continue cooking a few more minutes, then add the glass of vodka and cook over simmering heat a few more minutes so vodka cooks down and reduces a bit. Cover the skillet and place in the oven for about 40 minutes. While tomato-vodka sauce is getting nice and happy in the oven, bring a large pot of salted water to a boil and cook penne according to package instructions.  Then pour the drained penne into the skillet and mix well with the tomato-vodka sauce so the dish is well blended. Add a touch of heavy cream if you wish and a generous helping of freshly grated parmesan cheese. Serve to raves with a crisp, mixed green salad.