Heat oven to 350°F. Grease a 9-inch springform pan and line the bottom with parchment.
Toss sliced apples with lemon juice and cinnamon. Set aside to lightly macerate.
Whisk sugar and beaten eggs until pale and slightly thick, about 1 minute.
Stream in melted butter, then whisk in milk, vanilla, and lemon zest until smooth.
Combine flour, baking powder, and salt in a bowl. Whisk to evenly distribute.
Fold dry mixture into the wet ingredients just until a smooth batter forms.
Fold in half of the apples. Do not overmix.
Spread batter into the prepared pan. Arrange remaining apples on top, slightly overlapping.
Sprinkle with turbinado sugar if using. Bake 40–45 minutes until golden and set.
Cool 15 minutes. Release the ring, dust with powdered sugar, and slice to serve.