Preheat the overn to 350F.
Combine and sift together the flour with baking soda,baking powder and salt.
Beat the butter and sugar together until they turns soft, add the eggs one by one, add the vanilla extract.
Add slowly the sifted flour,buttermilk and turn as smooth batter.
Divide the batter into two portions, add unsweetened cocoa powder to a batter, mix well while the other portion dont disturb it.
Pour the vanilla cake batter in a greased bundt cake pan, and pour the chocolate cake batter on the top.
With a skewer make swirls and bake for 35-40 minutes.
