Preheat your oven to 350°F (175°C).

Grease your 9x9 inch baking pan with a bit of oil or line it with parchment paper.

In a mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt.

Make three wells in the dry mixture and add the oil, vinegar, and vanilla extract into each well. Pour the water over the entire mixture and stir until just combined.

Mix the batter gently until there are no dry spots.

Carefully pour the batter into the prepared baking pan.

Bake in the preheated oven for about 30 minutes or until a toothpick inserted in the center comes out clean.

Once baked, remove the cake from the oven and let it cool in the pan for 10 minutes.

Transfer the cake to a cooling rack to cool completely.