Preheat your oven to 175°C (350°F). Lightly grease your baking dish.
In a large mixing bowl, whisk together flour, sugar, salt, baking soda, and cocoa powder.
Make three small wells in the dry ingredients. Pour oil into one, vinegar into another, and vanilla extract into the third.
Pour water over everything and mix until smooth. Don’t over-mix, just until no dry flour remains.
Pour the batter into your prepared pan and bake for 30–35 minutes, or until a toothpick inserted in the centre comes out clean.
Meanwhile, prepare the icing: In a bowl, mix together powdered sugar and cocoa powder.
Add the vanilla and gradually add water, 1 tablespoon at a time, stirring until smooth and spreadable. Adjust the water to achieve your desired consistency.
Once the cake has baked, remove it from the oven and frost it only after it has completely cooled. Enjoy!