Heat oven to 350 degrees F. Line 2,8 or 9 inch cake pans with parchement paper, grease and flour bottom and sides of pans.
Sift together the flour, cocoa, baking powder, baking soda and salt. Set aside.
Cream the butter until fluffy. Gradually add the sugars scraping the bowl once or twice during this process.
Add the eggs, one at a time, scraping bowl after each addition.
Alternately add the flour mixture and sour cream in three additions. When adding the flour, pulse the mixer on and off to avoid flour flying everywhere. After all he flour and sour cream have been blended in, scrape bowl and mix for an additional minute.
Pour the batter(it is quite thick) into the cake pans and smooth the top with a spatula. Bake for 35 to 45 minutes or until a toothpick inserted the center cames out clean.