Preheat the oven to 350 degrees F. Spray two 8-inch round pans with nonstick baking spray with flour.
In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder and salt.
Add the espresso powder, eggs, 1/4 cup of the buttermilk, butter and vanilla to the flour mixture. Using an electric mixer, beat for 1 minute on medium speed, until blended. Scrape the sides and bottom of the bowl with a spatula. Beat on high speed for 2 minutes. Add the remaining buttermilk and beat on low speed for 15 to 30 seconds, until just blended.
Spread the batter evenly in the prepared pans, dividing equally.
Bake for 32 to 37 minutes or until a toothpick inserted into the center comes out with a few moist crumbs attached. Let cool in pans on a wire rack for 10 minutes. Run a knife around the edge of the pans, then invert the cakes onto a rack to cool completely.