Preheat oven to 325 degrees F (160 degrees C).
Peel, slice, and cut the Granny Smith Apple (1 1/2) into 8 wedges and sliced 1/8-inches thick.
Heat apples in a non-stick pan until translucent and slightly browned.
Add Calvados Apple Brandy (1 tablespoon) and Lemon Juice (1 teaspoon) and let rest for 15 minutes.
Whisk All-Purpose Flour (1 cup), Granulated Sugar (1 cup), Baking Powder (2 teaspoon) and Salt (1/2 teaspoon) together in a bowl.
Whisk Egg (1), Vegetable Oil (1 cup), Vanilla Extract (1 teaspoon) and Whole Milk (1 cup) in a separate bowl.
Pour dry ingredients into wet and mix until well combined. Transfer 1 cup of the batter into a separate bowl and set aside. Add Egg (2) to the remaining batter and whisk until well combined.
Transfer batter into a 9-inch spring form pan lined with parchment, or prepared with a natural shortening and floured. Lay apple slices evenly onto cake.
Whisk remaining All-Purpose Flour (2 tablespoon) into reserved batter. Spread this batter over the apples and batter in the pan. Sprinkle the remaining tablespoon of Granulated Sugar (1 tablespoon) evenly over the batter.
Bake 70 to 75 minutes in a spring form pan until cake is set, top is lightly browned, and a tooth pick comes out clean when inserted.
Let cool, and remove from pan. Dust with Powdered Confectioners Sugar (to taste).