This moist, tasty Chocolate Orange Marble Bundt can be made in any pan, but is extra festive stacked as a fun fall pumpkin! Drizzle it with ganache and orange glaze for even more flavor!
Preheat oven to 350F. Spray a 10-12 cup Bundt pan (or two 6 cup pans) with baking spray.
In a medium bowl, whisk cake flour, baking powder, baking soda, and salt. Set aside .
In the bowl of a stand mixer fitted with a paddle, cream butter and sugar on medium speed for 2 minutes until pale and fluffy. Add eggs one at a time on low speed, fully incorporating after each addition. Add vanilla and mix until well combined.
Alternate adding flour mixture and buttermilk, beginning and ending with flour, in 3 separate additions. Mix each addition until well combined. Do not overmix.
In a medium bowl, dissolve cocoa powder into very hot water. Mix 1/2 cup of cake batter into the cocoa mixture until combined, then add an additional 1 1/2 cups and mix well.
Fold 1/3 cup orange juice and zest into the remaining batter. Alternate adding orange and chocolate batters into the pans, swirling gently with a skewer. Tap the pan on the counter to evenly distribute.
Bake for 33-35 minutes or until a skewer inserted into the center comes out mostly clean. Remove from oven and place pans on wire rack to cool for 10 minutes. Turn the cakes out onto the wire rack to cool completely.
Orange Glaze
Whisk the powdered sugar, orange juice, and vanilla together to form a thick liquid. Whisk in more juice until desired thickness is achieved. Whisk in drops of food coloring until orange.
Chocolate Ganache
Place chocolate chips in a medium-sized bowl. Heat cream over stove top until barely simmering, or in the microwave for about 2 minutes. Pour cream over chocolate and allow to sit for 3-4 minutes, then whisk gently until combined and glossy. Add vanilla and stir until combined. Allow to cool to room temperature.
If creating a pumpkin bundt, flip one cake so the rounded side is down on a serving platter. Trim the cake so the surface is flat, then spread a thin layer of ganache on top. Repeat trimming on the other cake, then layer it on top of the other cake, creating a pumpkin shape.
Drizzle the ganache and orange glaze over the cake, then decorate with sprinkles if desired.