Preheat oven to 350°F. Line three 8-inch pans with parchment.
Whisk flour, sugar, cocoa, baking soda, baking powder, and salt.
Add eggs, buttermilk, and oil. Mix until combined.
Add hot coffee. Batter will look thin—totally normal.
Fold in orange zest and vanilla.
Divide batter into pans. Bake 25–30 minutes.
Cool completely.
Beat butter until pale. Add sugar slowly.
Mix in orange zest, juice, emulsion, and salt.
Frost chilled cake layers.
Pour cooled ganache drip over edges.
Add extra zest or candied oranges to finish.