Peel, core, and grate the apples using a box grater.
In a skillet over medium heat, combine the grated apples, brown sugar and cinnamon
Cook for about 10 minutes, stirring occasionally, until the apples are tender and caramelized.
Remove from heat and prepare the baking sheet.
Line your baking sheet with parchment paper.
Spread the cooked apple filling evenly over the parchment, creating a thin, uniform layer.
Next, separate the egg whites from yolks.
To a large mixing bowl, add egg yolks, vanilla extract, oil and milk. Whisk together to combine, add flour and baking powder. Mix everything.
In a separate bowl, beat the egg whites with sugar until stiff peaks form.
Carefully fold in the beaten egg whites into the batter, one-third at a time, until fully incorporated. Use a gentle folding motion to maintain the airiness.
Pour the batter over the apple filling on the prepared baking sheet.
Use a spatula to spread the batter evenly over the apples.
Bake in a preheated oven at 350°F (175°C) for about 15-20 minutes, or until the cake is golden and a toothpick inserted in the center comes out clean.
Once baked, remove from the oven and let it cool for about 5 minutes.
Place a sheet of parchment paper over the top of the cake.
Carefully flip the cake onto a wooden board or another baking sheet.
Gently peel away the parchment paper from the apples.
While the cake is still warm, carefully roll it up from one long end to the other, using the parchment paper to help. Let it cool completely in this rolled shape.
Once cooled, dust with powdered sugar.
Slice and serve!