Never forget to sieve the flour and cocoa powder as it will help to release the air in flour and will give a smooth pattern while cooking. Don't add cocoa powder in high quantity otherwise, it will be too strong to eat. You can add baking soda by combining baking powder to neutralize the flavor. In the place of lemon juice, you can also use vinegar. You can simply whisk the cake mixture in a clock or anti-clockwise direction. Chocolate frosting is optional, you can simply have the sponge cake. Don't bake the cake for too long as it will be prepared within 20 to 25 minutes.