Preheat the oven to 350F and line an 8x8 baking dish, or spray with non-stick oil.
Add the flour, sugar, cocoa powder, baking soda and salt to the 8x8 dish and stir until completely mixed.
Make two wells in the flour. In one, pour in the oil, and in the second, add the apple cider vinegar and vanilla. Pour the water over top, and then gently stir until a cake batter is formed.
Bake for approximately 28 minutes, until a toothpick poked in the center comes out clean. Allow to cool completely before coating with icing. Store in a sealed container on the counter for up to 3 days.
If you have access to vegan frosting at the store, you are more than welcome to use that. Alternatively, you can make your own frosting.
You can top your frosted cake with sprinkles, crushed nuts or seeds, or even fresh fruit if you have some.
If you're going to swap olive oil for something else, try to opt for another minimally processed oil such as coconut oil or avocado oil. However, to keep the recipe cost-effective, you can use any other oil of plant-based origin.
Equally, you can use a different type of sugar. A great alternative to brown sugar is coconut sugar!
For all of my gluten-free friends, you can try this recipe with all-purpose gluten-free flour. If the flour you are using doesn't contain xanthan gum as one of its ingredients, I would recommend adding a pinch of it when you mix your dry ingredients together.