- With the rack in the middle position, preheat the oven to 180 °C (350 °F). With softened butter, butter a 20-cm (8-inch) square baking dish.
- In the baking dish, combine flour, sugar, cocoa powder, baking soda and salt.
- Make a large and two small wells in dry ingredients.
- Pour oil into the large well. Pour vinegar in a small well and vanilla in the last one.
- Pour water into baking dish and stir with a fork just enough to moisten dry ingredients.
- Bake for about 30 minutes or until a toothpick inserted in the centre of the cake comes out clean. Let cool on a wire rack. Cut into squares.
- Serve cake with vanilla ice cream.