Follow these simple steps to create your Caramel Apple Upside Down Cake:

1. Preheat Your Oven: Set your oven to 350°F (175°C) and grease a 9-inch round cake pan.
2. Melt Butter: In a saucepan over medium heat, melt the unsalted butter. Once melted, add brown sugar and stir until combined.
3. Prepare Apples: Arrange the apple slices evenly in the bottom of the greased cake pan. Pour the butter and brown sugar mixture over the apples, making sure they are well-coated.
4. Mix Dry Ingredients: In a large bowl, whisk together the flour, granulated sugar, baking powder, salt, cinnamon, and nutmeg.
5. Combine Wet Ingredients: In another bowl, mix the milk, eggs, and vanilla extract until smooth.
6. Combine Mixtures: Gradually add the wet mixture to the dry ingredients, stirring until just combined. Do not overmix.
7. Pour Batter: Carefully pour the batter over the arranged apples in the cake pan, spreading it evenly.
8. Bake: Place the cake in the preheated oven and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
9. Cool: Allow the cake to cool in the pan for about 15 minutes. Then, run a knife around the edges and invert it onto a serving plate.
10. Serve Warm: If desired, serve with whipped cream or a scoop of vanilla ice cream for an extra treat.

These steps will guide you in creating a moist and flavorful Caramel Apple Upside Down Cake that everyone will adore.