We know that using an oven tangkring is a bit tricky. It doesn't have temperature and time setting. Then we have to really know the characteristic of our oven and stove. When I bake again the same cake the next day, I followed carefully the tip from maya. Here is my ways to handle my oven tangkring:
"Before we start making the batter of a cake, put the oven on a low heat. The fire from the stove just slightly touch the bottom of the oven. To bake a cake use the middle rack and don't open the door of the oven during the baking. The baking time is around 1 hour for 20 or 22 cm pan".
So, this is my second sponge cake. I used the same recipe as before, only skipped the emulsifier and used sunflower oil instead of melted butter or margarine. Can you see the difference between them? The taste of the second sponge is lighter than the first one, a bit close to a chiffon cake, maybe because of the oil. The texture is almost the same, fluffy and spongy.