Preheat oven to 350°F (175°C). Grease and line two 9-inch round cake pans with parchment paper.
In a large bowl, whisk together flour, sugar, cocoa, baking powder, baking soda, and salt.
Add eggs, buttermilk, oil, and vanilla. Beat until smooth. Slowly stir in hot coffee until batter is fully combined.
Divide the batter evenly between prepared pans. Bake for 30–35 minutes or until a toothpick comes out clean.
Cool cakes in pans for 10 minutes, then transfer to wire racks to cool completely.
Spread chocolate pudding over one cake layer, top with the second layer, and frost the entire cake.
Crumble any extra cake scraps over the top for a traditional blackout cake look.