For the Apples:

1. Peel and slice the apple into 1/4-inch thick slices, then sprinkle them with cinnamon and nutmeg. Give them a gentle stir to coat them evenly.

Preparing the Cake Pan:

1. Grease a 9-inch cake pan and line the bottom with parchment paper to prevent sticking.
2. Arrange the seasoned apple slices in a single layer on the bottom of the pan.

Making the Caramel:

1. Read through the instructions carefully before you begin.
2. Using a stainless steel saucepan, combine the sugar, water, and corn syrup or glucose. Stir gently until you achieve a wet sand consistency.
3. Brush the sides of the pan with water to prevent crystallization.
4. Heat the mixture over medium-high heat until it turns a light golden brown, then immediately pour it over the apples in the cake pan.

Preparing the Cake Batter:

1. Preheat your oven to 350°F.
2. In a medium bowl, whisk together the flour, baking powder, salt, cinnamon, and nutmeg. Set aside.
3. Using an electric mixer, beat the butter and sugar until light and fluffy. Add the eggs one at a time, followed by the vanilla extract.
4. Alternate adding the dry ingredients and buttermilk to the batter, mixing until just combined.
5. Spread the batter evenly over the caramel-coated apples in the cake pan.

Baking:

1. Bake the cake for about 35 minutes, or until a toothpick inserted into the center comes out clean.
2. Allow the cake to cool for 15 minutes before carefully flipping it onto a plate.