Sift maida flour, backing powder 3 times so they mix well.
Coat a baking tray with little butter and sprinkle flour and keep it aside. (you can use butter paper as well).
Break the egg and separate the egg yokes from egg whites.
Beat the egg white in a blender or by a beater until it foams well.
In a bowl add powdered sugar, unsalted butter and beat them until they become fluffy (creamy).
Now add the egg yolk and beat them until they come together (mixed well).
Now add the foaming egg white and beat well.
Now add vanilla essence, caraway seed, salt and mix well.
Now add sift maida flour little by little and mix well using folding technique. i.e. fold the batter in one direction with spatula to make folds.
Pour this batter to the baking tray and bake it for 45 minutes or until the cake is done (you can test if the cake is done by inserting a toothpick and when you pull it should come clean) at 180 Celsius in pre heated oven.