Sieve the flour, cocoa powder and the baking powder together and keep aside.
Preheat oven to 350° F before baking.
Take eggs in a large bowl and beat well till frothy. Take an electric mixer/ hand blender/ egg whisk whichever is available and comfortable for you. Keep the speed of the blender at medium and beat well scraping down the sides occasionally. Beating the eggs well is a crucial step in the cake preparation. Beat for about 5 – 7 min.
Now add the powdered sugar slowly to the above mixture spoon by spoon while beating continuously till a creamy froth is formed. This will take about 5 min.
Now turn the electric mixer’s speed to low, add the flour mixture slowly while beating to avoid lumps. Add a spoonful at a time. Beat for 5 min more.
Add butter/ vegetable oil slowly. Keep beating while scraping down for some time intermittently. Beat well at least for 5 – 10 min until the mixture turns fluffy with frothy.
Grease the cake pan with butter or vegetable oil. Transfer the cake batter to the pan. Gently tap the pan to let some trapped air to come out.
Place the cake pan in the oven and bake for 45 min.
A simple test to check whether the cake is baked completely or not is to insert a toothpick in the centre. The toothpick should come out clean without any batter sticking to it.
If the toothpick comes out with the batter sticking to it, you have it bake the cake for some more time probably 5 – 10 min more. Generally, this cake is done within 45 min.
Take the cake out of the oven and set it aside to cool.
Take a knife and run it between the edges of the pan and the cake slowly.
Now take a plate on which you want to unmould the cake. Invert it on the top of the pan.
Turn the pan over with the plate on the platform. Slowly lift the pan and keep aside.
Cut the cake into the desired shape and serve.