Peel, core, and thinly slice the apples. Toss with lemon juice to prevent browning and set aside.
Preheat the oven to 350°F (175°C). Grease a 9-inch springform pan or cake pan and line the bottom with parchment paper.
In a small bowl, whisk together flour, baking powder, cinnamon, and salt.
In a larger bowl, cream the butter and sugar until light and fluffy. Beat in the eggs, one at a time, then mix in the vanilla extract.
Add the dry ingredients in batches, alternating with the milk, and mix until just combined. Do not overmix.
Pour the batter into the prepared pan and smooth the top. Arrange the apple slices in a circular pattern or layer them gently over the batter. Sprinkle the optional cinnamon-sugar topping over the apples.
Bake for 45–50 minutes, or until a toothpick inserted into the center comes out clean and the top is golden and set. If the top browns too quickly, loosely cover with foil during the last 10–15 minutes of baking.
Let the cake cool in the pan for 10 minutes before removing the sides of the springform. Allow to cool completely or serve warm