Grease a 9" round cake tin with butter & dust it with flour. You may also grease the tin and line it with baking parchment if you wish.
Preheat the oven to 175 degrees C.
Sift the flour & baking powder thrice. Keep aside
Beat the egg whites in a bowl till fluffy. In a separate bowl beat the egg yolks till creamy
In a bowl, beat the butter & sugar together till pale and fluffy. Beat in the egg yolks
Add the beaten egg whites and either fold in with a spatula or use the electric whisk on low speed to mix in
Next, add the milk & the flour alternatively & fold gently till everything is used up
Pour the batter into the prepared tin and bake in the preheated oven for about 45-50 minutes or till the skewer inserted comes out clean.
Remove from the oven and let the tin cool on a wire rack for about 12-15 minutes. Then invert the cake onto the rack and let it cool completely. Cut and serve. Store the cooled cake in an airtight container.