How to make
Beat the egg whites with a pinch of salt into a fluffy mixture. Gradually add the sugar, by stirring constantly, until the mixture becomes even thicker.
Beat the yogurt with the oil separately and add the mixture in portions to the egg whites, by stirring gently with a silicone or wooden spoon.
Sift the flour with the baking powder in portions to the fluffy mixture, by trying to keep the egg whites as airy as possible while mixing. To do this, make circular motions in one direction only.
Finally, add the chopped walnuts and the pieces of quinces.
* For the quinces there are two options - to use pieces from jam or boil them with a little sugar and a little water. It's not good to use them raw for this sponge cake. I poured the diced quince jam in a mold.
Pour the mixture into a greased and floured cake tin and bake for about 30 minutes or until it is fully baked in a preheated oven at 350°F (175°C).
Never open the oven door for the first 20 minutes.
Wait for the sponge cake to cool before removing it from the cake tin. Optionally, you can sprinkle it with powdered sugar and garnish it with more walnuts.
The fluffy sponge cake with quinces and walnuts is ready.
