Chocolate Orange Marble Cake

Step 1: Prep

Start by preheating the oven to 350°F. If using a convection oven, reduce the temperature to 325°F instead.

Grease a 12-cup bundt pan very thoroughly with softened butter, making sure to coat all the crevices well. Dust the pan with flour and shake out the excess. Bundt cakes are beautiful, but they can stick very easily if the pan isn’t properly prepared.

Step 2: Make the orange sugar

To make the orange sugar, combine the granulated sugar and orange zest in a bowl. Rub the zest into the sugar with your fingers until the sugar becomes fragrant and slightly damp. This step helps release the oils from the orange peel and gives the cake a much stronger orange flavor.

Step 3: Beat the butter and sugar

In a large bowl, beat the butter with an electric mixer on medium speed for about 2 minutes until creamy. Add the orange sugar and continue beating for another 2 minutes until the mixture becomes lighter and fluffy. Add the eggs one at a time, mixing well after each addition. Scrape down the bowl as needed.

Also, in a medium bowl, whisk together the flour, cornstarch, salt, baking powder, and baking soda. Set aside.

Step 4: Add the sour cream and orange juice

Mix in the sour cream and orange juice on low speed until combined.

Step 5: Add the dry ingredients and milk

Add half of the dry ingredients and mix briefly. Pour in the milk and mix again. Add the remaining dry ingredients and mix just until incorporated. I usually finish folding the batter with a spatula to avoid overmixing, which can make bundt cakes dense instead of soft.

Step 6: Split the batters

Transfer about one-third of the batter to a separate bowl. Add the cocoa powder and milk and stir until smooth. If the chocolate batter seems too light in color, you can add a bit more cocoa powder and another splash of milk if needed.

Step 7: Assemble the cake

To assemble the cake, spoon some of the orange batter into the prepared bundt pan, then spoon some chocolate batter on top. Continue alternating the batters throughout the pan until all the batter has been used.

Step 8: Swirl

Use a butter knife or spatula to gently swirl the batters together a few times. Don’t overdo it or the marble effect can disappear completely.

Step 9: Bake

Bake the cake for 55 to 65 minutes, depending on your oven. If the top starts browning too much before the center finishes baking, loosely tent the pan with foil for the remaining bake time.

The cake is ready when the top springs back lightly and a toothpick inserted into the cake comes out clean.

Step 10: Orange Syrup

While the cake bakes, prepare the orange syrup.

Combine the orange juice, sugar, and orange peel in a small saucepan over medium heat. Bring the mixture to a boil just until the sugar dissolves completely, then remove from the heat.

When the cake comes out of the oven, let it cool in the pan for about 5 minutes. Use a fork or skewer to gently prick the top of the cake.

Remove the orange peel from the syrup and slowly pour the warm syrup all over the cake while it’s still warm. Let the cake sit in the pan for another 15 minutes so it can absorb the syrup properly before flipping it out onto a serving plate or cooling rack.

Step 11: Orange Chocolate Ganache

Place the heavy cream and orange peel in a small saucepan and heat until steaming but not boiling.

Step 12: Strain and pour

Remove from the heat, strain out the orange peel, and pour the hot cream over the chopped milk chocolate. Let it sit for 1 minute before whisking until smooth and glossy.

Step 13: Allow the ganache to cool, then spread it on the cake!

Allow the ganache to cool for about 30 minutes until slightly thickened but still pourable. Drizzle it over the cooled cake and finish with fresh orange zest if desired.