In a large bowl, put water, extract (if using), eggs, melted butter and sour cream. Mix well with paddle attachment.
Add cake mix, sugar, cake flour, and salt.
Mix with paddle attachment at medium speed for approximately 2 minutes, or until most lumps are worked out. It is not necessary to work out all the lumps.
Pour into prepared pans and bake at 325 until a toothpick inserted into the center comes out clean, or with just a crumb or two clinging to it. For two 8" or 9" rounds this is around 40 minutes, but every oven is different. Your cake is getting close to done when you can smell it. If it looks close I like to give the rack a little shake. If the center jiggles at all, it's not ready. If it doesn't jiggle, go ahead and test with the toothpick.
Cool for 7-10 minutes in pan, then turn out onto cooling rack. If you experience problems with sticking, you may wish to line your baking pans with parchment paper.
