Preheat your oven to 350°F (175°C). Prepare two 8-inch round baking pans by lining the bottoms with parchment paper and lightly greasing the sides with non-stick spray.

In a large mixing bowl, whisk together granulated sugar, all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt until evenly combined.

Add the large eggs, buttermilk, vegetable oil, and vanilla extract to the dry mixture. Using an electric mixer, mix on medium speed for about 2 minutes until the batter is smooth and well blended.

Carefully stir in the boiling water or hot coffee into the batter until fully combined.

Divide the batter evenly between the two prepared baking pans. Bake for 30-35 minutes or until a toothpick inserted comes out clean.

Once baked, allow the pans to cool for about 10 minutes. Then transfer the cakes to a cooling rack to cool completely.

In a mixing bowl, combine melted unsalted butter and unsweetened cocoa powder. Gradually add the powdered sugar and milk while whisking until smooth and creamy.

Place one cooled cake layer onto a serving plate. Frost the top generously, then stack the second layer and frost the top and sides.

Slice and serve the cake, optionally with vanilla ice cream or fresh berries.