Preheat the oven to 356°F (180°C).
Grease and lightly flour a 9-inch (22 cm) round cake pan.
Peel, core, and thinly slice the apples.
Toss the apple slices with the lemon juice to prevent browning.
In a large mixing bowl, beat the eggs, sugar, lemon zest, and a pinch of salt using a hand mixer for about 5 minutes, until pale, thick, and fluffy.
Gradually fold in the sifted flour and baking powder.
Pour in the milk and gently mix until a smooth batter forms. Avoid overmixing.
Fold two-thirds of the apple slices into the batter.
Pour the batter into the prepared cake pan.
Arrange the remaining apple slices neatly over the top with the flat sides facing down.
Sprinkle with the optional tablespoon of sugar for a lightly caramelized finish.
Bake the Healthy Apple Cake for approximately 35 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool completely on a wire rack.
Dust with powdered sugar just before serving, if desired.