In a bowl, mix sugar, water, and oil with a whisk until dissolved.

Add baking powder and salt, and mix again.

Separately, beat the egg whites until stiff peaks form and gradually fold them into the batter, mixing from bottom to top.

Peel the apples, cut them into small pieces, and add them to the batter.

Pour the batter into a baking pan and bake at 350°F (180°C) for 50-60 minutes. Always do the toothpick test to check for doneness.

Let the cake cool before removing from the pan, dust with powdered sugar, and serve.