In two bowls, separate egg whites and egg yolks & set aside.
In mixing machine, add egg whites and beat until stiff peaks form.
During mixing gradually add egg yolks.Shift flour and cocoa powder in a bowl.
Gradually add dry ingredients and gently fold with the help of a spatula until well combined.
Mix oil, milk, and vanila in a bowl, mix some better in the oil mix then mix in the batter carefully.
Grease a 6 inch baking pan with butter and place butter paper.
Now pour the batter into a prepared baking pan, run a wooden stick clockwise in the pan tape 2 to 3 times on the surface, bake preheated at 200 C for 25 minutes.
Remove the cake from the oven, Transfer the cake to the wire rack and let it cool.