• Before making the batter, whisk the cocoa powder and hot water in a small bowl and set aside for later.
• Also, preheat the oven to 350F and line a 1-pound loaf pan with parchment paper or lightly grease it.

Make the cake batter:

• Start by adding the oat/soy milk and apple cider vinegar to a large mixing bowl and whisking them together. Let sit for 2-3 minutes until the milk begins to curdle to form the "vegan buttermilk".
• Next, add the remaining wet ingredients to the mixing bowl including the sugar, yogurt, melted vegan butter, and vanilla bean paste. Whisk together until smooth.
• Then, add the dry ingredients to the bowl starting with the all-purpose flour and then layering the baking powder, baking soda, and salt on top. Gently whisk into a smooth batter, keeping in mind that some clumps are okay.
• Take 1 ¼ cups of the vanilla cake batter and add it to a separate large mixing bowl. Then, add cocoa mixture to one bowl of the batter and mix together until completely brown with no streaks.

Assemble & bake the cake:

• Use two cookie scoops or large spoons to alternate dollops of the vanilla batter and chocolate batter into the parchment-lined loaf pan. Once all the batter has been added to the pan, gently swirl a knife through the batter- making sure not to overmix. This helps to create distinct marbled swirls when the bread bakes.
• Add the loaf pan to the oven and bake for 50-52 minutes until cooked through and browned on top.

Serve & enjoy!

• Take the loaf pan out of the oven and let the cake cool in the pan for about 5 minutes.
• Run a knife along the outer edges to gently remove any stuck bits. Then, remove and transfer the cake to a wire rack to cool completely before slicing.
• Slice the cooled cake into 8 slices using a serrated knife to enjoy!