Preheat the oven to 350 degrees and spray two 8 inch (or three 6 inch) cake pans with non-stick spray and line with parchment paper.
In a large bowl, combine flour, cocoa powder, baking soda, baking powder, and salt. Whisk to combine, then set aside.
In another large bowl, combine sugar, eggs, yogurt, oil, and vanilla. Using an electric hand-held mixer, mix on medium low speed until fully incorporated. Add half of the flour mixture and half of the buttermilk. Mix on low speed until just combined. Then add the rest of the flour and buttermilk and mix until fully combined.
Divide batter between the prepared pans and bake for 20-22 minutes, or until the centers are set and a toothpick inserted into the center of each cake comes out clean. Let the cakes cool in the pans for 10 minutes, then turn out onto a wire rack to cool completely.