1. Make the Chocolate Cake Preheat oven to 350°F (175°C). Grease and line three or four 8" round pans. Whisk dry ingredients in one bowl. In another, mix sugar, eggs, buttermilk, oil, and vanilla. Combine both and stir in hot water. Divide into pans and bake for 30–35 minutes. Cool completely.
2. Prepare the Orange Filling Beat butter until fluffy. Add powdered sugar gradually, then mix in orange zest, juice, and optional coloring. Beat until smooth and vibrant.
3. Make the Ganache Heat heavy cream until simmering, then pour over chocolate chips. Let sit for 2 mins. Stir until smooth. Let cool slightly to thicken.
4. Assemble the Cake Layer cake rounds with orange filling between each. Smooth sides if desired. Pour ganache over top and let it drip down sides.
5. Decorate Top with orange slices or chocolate curls. Chill before slicing for clean layers.