Preheat the oven: Preheat your oven to 350°F (175°C). Grease and flour an 8×8-inch or 9×9-inch baking pan or line it with parchment paper.

1. Combine dry ingredients: In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt until well combined.
2. Add wet ingredients: Create three wells in the dry mixture. In one well, add the vanilla extract; in another, add the vinegar; and in the third, add the vegetable oil. Pour the cold water over the mixture and stir everything together until smooth and fully combined.
3. Bake: Pour the batter into the prepared baking pan and spread it out evenly. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
4. Cool and serve: Allow the cake to cool completely in the pan before serving. You can enjoy it as is, or frost it with your favorite frosting or a dusting of powdered sugar.