Preheat oven to 350°F. Grease three 8-inch pans and line with parchment paper.
In a small bowl, combine flour, cocoa powder, baking soda, salt, and espresso powder.
In a large bowl, combine oil, sugar, eggs, and vanilla extract.
Add 1/2 of the flour mixture to the sugar mixture and stir until combined. Add the buttermilk and then the remaining flour mixture.
Pour batter into prepared cake pans and bake 20-25 minutes or until a toothpick inserted in the center comes out clean. Let cool completely before frosting.