I do not know if from the photo you can appreciate what spongy what is this cake. It's a show. It has eggs, cream, and the grated skin of a lemon, very basic ingredients with which we obtain an exceptional result.
No butter or oil because born It is what provides the fat. On the surface we will put a little sugar which will create a delicate scab crunchy. Encourage yourself to try it because you are going to love it.
More information - How to flavor sugar