Whip the eggs with the sugar until frothy and fluffy. Gradually add the yoghurt and the previously melted (and cooled) butter, continuing to whisk. Add the sifted flour, starch and baking powder (this makes it easier to combine them with the dough). If the dough is too difficult to work with, you can add half a glass of milk. When the mixture is smooth and free of lumps, pour it into a greased and floured 24 cm cake tin. At this point, you can sprinkle the surface with plenty of granulated sugar if you wish. Bake in a preheated, static oven at 180 degrees for about 40 minutes.