I used to have a recipe that I got from an old employer for vanilla cupcakes and cake. I have done many google searches and have never found that recipe. It used club soda instead of milk, and the resulting cupcakes stayed soft and moist like they were freshly baked for days. You could also swap the club soda for other carbonated liquids, like champagne. I know it used cake flower and you have to whip the egg whites seperately if that helps. 

I have found a lot of tasty vanilla/yellow/white cake recipes that turn out well, but none of them stay as soft as for as long as this recipe. Plus, the carbonated liquid allowed for a lot of flavor variations. I would love to have this recipe again. Does it ring any bells?

AI think this may be it..

http://www.yummly.com/recipe/White-Cake-Recipezaar_8?columns=1&position=8%2F19