Preheat oven to 180°C. Prepare four 7" cake pans by greasing and flouring them. Reserve.
In a medium bowl, add soy milk, apple cider vinegar and whisk until foamy. Let it rest for 8 minutes.
Meanwhile, in a large bowl sieve flour, corn starch, baking powder, baking soda and salt. Reserve.
Bring back the bowl with the milk and apple cider vinegar, and add orange juice, orange zest, vanilla, and give it a mix. Add sugar and stir. Finally, add melted margarine/vegan butter (lukewarm) and mix.
Add the previous mix to the dry ingredients and mix until no flour lumps are visible. Don't overmix, otherwise it could affect the cake texture.
Divide the batter evenly between the 4 cake molds and bake for 30-34 minutes or until you insert a toothpick in the center of the cake and it comes out clean. I bake two pans at a time due to my oven model, but if you can pop all of them in at once, go for it. Just double check the baking time.
Once they're cooked, remove from the oven and let them cool down for 15 minutes (still in the cake pans). Afterwards, tap the pans a little bit and flip them over (you can use a cooling rack to help yourself flipping the pans).