Place the water and orange juice in a bowl of a food processor (or place the ingredients in a bowl and combine with a whisk). Add the sugar and whisk until completely dissolved.
With the machine working, slowly add the oil and whisk until fully combined.
Add the vanilla and whisk to combine.
Add the flour, baking powder and orange zest and keep whisking until smooth.
Pour the batter into the prepared pan and bake for 15 minutes or until a toothpick comes out clean.
Video
Notes
To make it gluten-free, replace cake flour with 175g potato flour and 175g corn starch.
For the matcha version, add1 tbsp matcha powder and replace orange juice with non-dairy milk (I used almond). Orange zest is also not required.
For the chocolate version, add 1 tbsp raw cacao powder and replace orange juice with non-dairy milk (I used almond). Orange zest can be used if you like.
The food processor simplifies the method but it’s totally fine to whisk the ingredients by hand.