This Chocolate Orange Cake is a single layer of moist, fluffy chocolate orange cake topped with chocolate orange buttercream! You will love this cake's depth of flavor!
Preheat oven to 350° F. Grease an 8" cake pan (see note) and set aside.
In a medium bowl, combine the dry ingredients (flour, cocoa [see note], baking soda, baking powder, and salt). Set aside.
In a large bowl, combine the sugar and orange zest. Rub the zest into the sugar with your fingertips to release the oils from the zest.
To the sugar mixture, add the remaining cake ingredients: vegetable oil, egg, buttermilk (see note), orange juice, water, orange oil (see note), and chocolate extract (see note). Whisk thoroughly to combine.
Add the flour mixture and whisk until smooth. Pour the batter into the prepared pan.
Bake 23-25 minutes, or until a toothpick inserted in the center comes out clean, or with a few moist crumbs attached. I turn the pan around in the oven halfway through baking to help ensure an even bake.
Cool cake 10 minutes in the pan, then turn out onto a wire rack to cool completely.
For Buttercream
In a small bowl, combine the cocoa powder (see note) and powdered sugar. Set aside.
In the bowl of a stand mixer, combine the butter and orange zest. Beat until smooth and creamy.
Add the orange oil (see note), chocolate extract (see note), and salt. Mix to combine.
Gradually add the sugar/cocoa mixture and mix until incorporated. Add one tablespoon of milk, then check the consistency of the buttercream. Add more milk as necessary (a tablespoon at a time) until you reach the desired consistency.
Frost the cake with the buttercream, adding fresh or dried oranges as garnish, if desired.
You can store your completed Chocolate Orange Cake covered on your counter for up to two days, or covered in your refrigerator for up to five days.You can also make the cake in advance and, wrapped well, it can be stored in the freezer for up to three months. Just thaw, then add the buttercream.Enjoy!
Notes
Note on cake pan: I used an 8" square pan for this recipe, but an 8" round cake pan will also work (and the cake will bake up in the same amount of time).Note on dark (dutch process) cocoa: *Not* the same as natural cocoa powder, dark (or dutch process) powder is darker and smoother.Note on orange oil: I love using orange oil to heighten the orange flavor in the cake. I've found that the oil has more concentrated flavor than orange extract. If you'd prefer not to buy orange oil, you can use orange extract, or just add a bit more zest to your batter.Note on chocolate extract: I highly recommend this (sometimes overlooked) extract! It lends an amazing depth of flavor to chocolate baked goods! You can even make yourself some Homemade Chocolate Extract for next time!Note on buttermilk: If you don't have buttermilk on-hand, you can pour ¼ teaspoon vinegar OR lemon juice in a liquid measuring cup, then add enough milk (I find that 2% milkfat or greater works best) to come up to the ¼ cup line. Let sit for 5 minutes, then it's ready for use!