Directions

1. Preheat oven to 350 degrees. Make the filling: Stir together sugar, coffee, and cocoa powder in a small bowl; set aside.
2. Butter a 10-inch (12-cup) Bundt pan. Dust with flour, and tap out excess. Make the batter: Whisk flour, baking powder, baking soda, and salt in a medium bowl. Put butter and sugar into the bowl of an electric mixer fitted with the paddle attachment. Mix on medium-high speed until pale and fluffy, 3 to 4 minutes. Reduce speed to medium. Mix in eggs, one at a time. Mix in flour mixture in 3 batches, alternating with sour cream. Add vanilla, and mix 1 minute.
3. Spread 1/3 of the batter into prepared pan. Sprinkle with half the filling. Spread another third of the batter on top, followed by the remaining filling. Spread remaining batter over top. Run a thin knife through batter to marbleize.
4. Bake until a cake tester inserted into center comes out clean, 35 to 38 minutes. Let cool 30 minutes. Invert onto a plate.