Sieve All Purpose Flour along with baking Powder and Baking Soda two times.
Separate the Egg White from the Yolk and place those in two separate bowls.
Beat Egg White using a Blender with whisking attachment till the Egg white forms medium peaks (as shown in the Picture) and keep that aside. It took me around 1 minute to make the medium pick.
Now take Oil along with the Sugar Powder in a bowl and mix it using the mixing attachment till sugar dissolves and the mixture reaches a creamy consistency.
Now add the Egg Yolk to the Sugar and Oil mixture and fold lightly.
Add both Lemon Zest and Lemon juice to the mixture.
Add Buttermilk as well while mixing.
Now add All Purpose Flour little by little to the Egg-Sugar-Oil mixture and mix lightly to fold it. Do not over-mix.
Finally, add Egg White to the batter and fold very lightly to keep air bubbles within the mixture as much as possible to make the cake fluffy.
Now take the desired Cake tin (I have used my rectangular cake tin for this) and spray some oil on this and then place a piece of baking paper and set properly.
Pour the Cake batter into the tin to ⅔ height.
Now place the Cake tin(s) in the Oven and bake for around 15-20 minutes in 180 degrees C.
Check whether the baking is done or not after 15 minutes by inserting a fork or toothpick. If it comes out clean, then the cake is ready. It took me 20 minutes to bake the cake.
Take the cake out of the oven and cool it on a wire rack.
Cut the cake into pieces to serve.