Put all the cake ingredients: flour, sugar, baking powder and soda, cocoa, butter, eggs, vanilla, and sour cream into a food processor and process until you have a smooth, thick batter. Scraping down the sides so that everything is mixed smoothly.
Divide this batter, using a rubber spatula to help you scrape and spread, into the prepared tins.
Bake until a cake tester comes out clean, which should be about 35 minutes, but it is wise to start checking at 25 minutes. Also, it might make sense to switch the 2 cakes around in the oven halfway through cooking time.
Allow the cakes to cool completely. Don't worry about any cracks as they will easily be covered by the frosting later.