Preheat the oven to 355°F (180°C). Grease bundt cake pan** with oil or vegan butter and lightly dust it with flour. Set aside.

In a bowl, combine all-purpose flour, baking powder, baking soda, and a pinch of salt. Mix with a whisk and set aside.

In a large bowl, using a whisk, combine granulated sugar, sunflower oil, and vegan sour cream. Add oat milk and apple cider vinegar and mix to combine. Sift in the flour mixture and mix everything with a spatula until incorporated. Don’t overmix the batter.

Using a spoon or cookie scoop, alternate adding yellow and chocolate batter to the pan. Then gently swirl the batter using a skewer or knife.

Bake in preheated oven for 35 minutes, or until a skewer inserted in the middle comes out clean. Remove from the oven and allow to cool in the pan for about 15 minutes. Then turn it upside down and let cool completely on a cooling rack.

Before serving, dust the cake with powdered sugar.