Found this recipe at SmittenKitchen. This cake just bowled me over! Super moist and flavorful, but really light. It's hands-down the best from-scratch cake I've ever made, so I posted here for safekeeping!
Butter the bottoms and sides of three 8-inch round cakepans.
Line the bottom of each pan with a round of parchment or waxed paper and butter the paper.
Sift the flour, sugar, cocoa powder, baking soda, and salt into a large bowl, and whisk to combine them well.
Add the oil and sour cream and half the water, whisk to blend; then gradually beat in the remaining water.
Blend in the vinegar and vanilla, and whisk in eggs, beating until well blended.
Scrape down the sides of the bowl and be sure the batter is well mixed.
Divide among the 3 prepared cake pans.
Bake for 30 to 35 minutes, or until a cake tester or wooden toothpick inserted in the center comes out almost clean.
Let cool in the pans for about 20 minutes. Invert onto wire racks, carefully peel off the paper liners, and let cool completely.
(Note: These cakes are very, very soft. I found them a lot easier to work with after firming them up in the freezer for 30 minutes. They’ll defrost quickly once assembled. You’ll be glad you did this, trust me.).
Frost with desired frosting. For the Peanut Butter Frosting and Glaze with the original recipe: http://smittenkitchen.com/2008/08/chocolate-peanut-butter-cake/.