Preheat the oven to 180 °C (356 °F).
Grease and flour an 18 cm (7-inch) diameter springform pan.
Add eggs and salt to a bowl. Whisk for 1 minute.
Add 100 g sugar and whisk until light and fluffy.
Add the flour in 3 batches, continuing to whisk.
Add baking powder, vanilla, milk, butter, and whisk.
Add lemon zest and stir. Set aside.
Peel and cut the apples into thin slices. Mix with lemon juice.
Add the apples to the batter.
Pour the mixture into the springform pan.
Sprinkle with 2 tablespoons granulated sugar.
Bake in the preheated oven for 40–50 minutes, until the top is golden brown and a toothpick inserted into the center comes out clean.
Allow to cool completely without removing the cake from the pan.
Sprinkle with icing sugar before serving the cooled cake.