Preheat the oven to 350°F (175°C) and line two 9-inch round cake pans with parchment paper, greasing the sides.

In a large mixing bowl, sift and whisk together the flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt until evenly combined.

In a medium bowl, whisk the eggs, cooled brewed coffee, vegetable oil, vanilla extract, and buttermilk until smooth.

Pour the wet ingredients into the dry ingredients and stir with a rubber spatula until just combined, leaving the batter slightly lumpy.

Divide the batter evenly between the prepared pans and smooth the tops with an offset spatula.

Bake for 30 to 35 minutes until a toothpick inserted in the center comes out with moist crumbs and the tops spring back.

Let the cakes cool in the pans for 15 minutes, then invert onto cooling racks, remove parchment, and cool completely for about 1 hour.

In a large bowl, beat the softened butter on medium speed for 2 minutes until light, then gradually add cocoa powder and powdered sugar in batches, beating well after each addition.

With the mixer on low, pour in the heavy cream, vanilla extract, and salt, then beat on medium speed for 2 minutes until fluffy and spreadable.

Place one cake layer on a serving plate, spread about 1 cup of frosting over it, then top with the second layer, flat side down.

Frost the top and sides of the cake with the remaining frosting, using an offset spatula to create smooth or textured swirls.

Chill the frosted cake in the refrigerator for at least 2 hours before slicing to set the frosting and achieve clean cuts.