Preheat oven to 350 degrees Fahrenheit. Grease the bundt pan.

In a stand mixer or hand mixer beat egg whites until fluffy add half of the sugar gradually until mixture is stiff peaks. Add vanilla sugar and fold with a spatula gently until fully incorporated.

In a large bowl, whisk together the egg yolks, orange juice, and oil until the mixture is foamy and light. Then add the almond flour, potato starch, baking powder, salt, and 3/4 cup of the sugar mixture until the mixture turns into a thick batter. Pour the batter into the meringue mixture. Using a spatula, gently fold the mixture until it is incorporated. Remove 1/4 of the batter into a medium-sized bowl and set aside. Pour the rest of the batter into the bundt pan evenly.

To the medium-sized bowl of batter, add the cocoa and 1/4 cup of sugar. Fold with a spatula until fully incorporated. Pour all of it into the pan. Using a knife, swirl the chocolate mixture into the vanilla mixture lightly. Bake for 35 minutes. Once done, let cool. Enjoy!!