Preheat the oven to 350 degrees F. Spray three 8-inch or four 6-inch round cake pans with nonstick spray. Line the bottom of each pan with parchment paper and spray the pans again.
Combine the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined. Add the zest and mix until combined.
In another bowl, combine the buttermilk, oil, eggs, coffee or water and vanilla.
With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a rubber spatula.
Pour the batter evenly into the prepared pans and bake for about 16-18 minutes.
Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely.
Wrap in plastic wrap and chill until ready to use. You're still going to want to level your cake layers to ensure a completely even surface for frosting and stacking.
In a microwave safe bowl, heat the heavy whipping cream for about one minute. Pour the heated cream over the chocolate chips and stir until the chocolate chips are melted. Set aside
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter on medium-high speed for 2 minutes.
Turn the mixer to low and gradually add the powdered sugar, orange emulsion and pinch of salt.
With the mixer on low speed, add the chocolate ganache. Beat for another 3 to 5 minutes on medium-high.
Before frosting your cake, give the frosting a good stir with a wooden spoon to push out any air bubbles.