Mix oil, ¾ cup of non-dairy milk, vanilla extract, granulated sugar, baking powder, salt, and orange juice in a large bowl.
Once those ingredients have been well combined, add in the flour and stir until incorporated.
Divide the cake batter into two bowls. Add the orange zest to one bowl. Stir until combined.
Add the cacao powder and one tbsp of the non-dairy milk to the bowl. Stir until well combined.
Take the prepared mold, and pour some of the chocolate batter, followed by some of the orange batter. Repeat this process for the rest of the mixture.
Bake until inserted toothpick comes out clean. About 45 minutes.