Preheat oven to 356°F (180°C). Grease and flour a 9-inch round cake pan.
Peel, core, and thinly slice the apples. Toss with lemon juice to prevent browning.
In a large bowl, beat eggs, sugar, lemon zest, and salt until thick and creamy (about 5 minutes).
Gently mix in flour, baking powder, and milk until just combined.
Fold in two-thirds of the apples.
Pour batter into the pan and arrange remaining apple slices on top.
Sprinkle with sugar if desired.
Bake for 35 minutes or until golden and a toothpick comes out clean.
Cool completely and dust with powdered sugar before serving.