In your stand mixer, beat the eggs, sugar, lemon zest, and salt until thick and creamy before adding in the flour, baking powder, and milk. Continue to beat until combined before folding in about two-thirds of the apples. Then, pour the batter into your pan and artfully arrange the remaining sliced apples on top. If desired, sprinkle with a tablespoon of brown sugar before baking for about 35 minutes or until golden brown and done in the middle. Remove from the oven and dust with powdered sugar before serving!