As per the name suggest sponge cake is so much spongy that toothless person can also eat and this cake is easy to bake and no required more ingredients you can make this at home also.

Whisking butter and sugar together is the one of tip to make the cake spongy and fluffy. Whisk butter and sugar for long until the mixture becomes yellow and fluffy because of incorporation of air.

Most cakes will call for a leavening agent like baking powder or baking soda. These create the bubbles need for the cake to rise. If flour that you use is self-raising, no need to add extra.
This cake is classic, simple Vanilla Sponge Cake that is made with basic ingredients like eggs, milk, butter, flour, sugar, vanilla essence, baking powder and salt(if needed).