Preheat the oven to 350°F.
Grease an 8-inch cake pan or 8-inch springform pan with baking spray.
Line the bottom and sides of the pan with parchment paper.
Spray the parchment paper lightly with baking spray.
Place the prepared pan on a small baking tray and set aside.
In a small bowl, combine the sliced almonds, light brown sugar, and cinnamon.
Stir until evenly mixed, then set the topping aside.
In a separate bowl, combine the all-purpose flour, baking powder, and fine salt.
Mix well and set aside.
In a large mixing bowl, beat the room-temperature butter and granulated sugar together for 2 to 3 minutes, or until light and fluffy.
Reduce the mixer speed to low.
Add the eggs one at a time, beating well after each addition.
Add the dry ingredients in 3 additions, alternating with the milk in 2 additions.
Begin and end with the dry ingredients.
Mix only until the batter is combined.
Use a rubber spatula to scrape the sides and bottom of the bowl.
Gently mix once more to ensure the batter is smooth and evenly blended.
Pour the batter into the prepared cake pan.
Spread the batter evenly with a spatula.
Arrange the thinly sliced apples over the top of the batter.
Press the apple slices slightly into the batter so they fit securely.
Sprinkle the prepared almond, brown sugar, and cinnamon topping evenly over the apples.
Bake for approximately 1 hour, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Remove the cake from the oven.
Allow it to cool slightly before removing it from the pan.
Serve warm or at room temperature with whipped cream, if desired.