Peel and chop the apple into small pieces. Cook it in a saucepan with cinnamon powder and sugar until the sugar dissolves.

Transfer the cooked apple filling to a bowl and let it cool completely.

Cream the softened butter with a whisk, gradually adding sugar in three portions until light and fluffy.

Separate egg yolks and whites. Add yolks one at a time to the butter mixture, mixing well.

Gradually add the egg whites in three portions, mixing well each time. Add a few drops of vanilla oil and mix.

Sift cake flour and baking powder into the mixture. Fold gently using a spatula in a cutting motion.

Add milk and mix gently. Fold in the cooled apple filling until evenly distributed.