Place the egg whites in a large bowl and beat them until very stiff using an electric mixer.

In another bowl, mix together the water, sugar, and oil using a kitchen whisk.

Gradually add the sifted flour, cocoa, and baking powder to the liquids. Add vanilla for flavor. Mix the ingredients until you get a smooth, lump-free batter.

Gently fold the beaten egg whites into the batter using an upward motion.

Pour the batter into a greased and floured 9-inch cake pan. Bake in a preheated static oven at 350°F (180°C) for 40 minutes. Perform the toothpick test.