Air Fryer Upside Down Caramel Apple Cake

Preheat your air fryer to 320 degrees F and grease a cake pan or springform pan.
Melt the 1/4 cup butter, 3/4 cup light brown sugar, 1 teaspoon pure vanilla extract 1/2 teaspoon ground cinnamon, and 1/2 teaspoon kosher salt in a small saucepan over medium-high heat. Stir and cook for 2 minutes until the mixture thickens. Pour the caramel sauce into the bottom of your prepared pan. Arrange the 2 medium apples wedges on top of the caramel sauce in the pan.
In a medium bowl, combine the 1 3/4 cup all-purpose flour, 3/4 teaspoon baking powder, 1 teaspoon ground cinnamon, 1 teaspoon ground nutmeg, and 1 teaspoon kosher salt in a bowl until combined.
In a large bowl, use an electric or hand mixer to blend the 1/2 cup butter 3/4 cup granulated sugar and 1/2 cup light brown sugar until creamy. Stir in the 2 large eggs one at a time until combined. Add in the 1 teaspoon pure vanilla extract, followed by half of the dry ingredients until incorporated. Mix in the remaining dry ingredients, followed by the 3/4 cup milk until just combined.
Spread the batter over the caramel apple mixture. Bake in the air fryer for 20-30 minutes, or until a toothpick inserted comes out clean. If the toothpick comes out with uncooked batter, return to the air fryer and bake for several more minutes. Once the cake has finished baking, allow it to fully cool before removing it from the pan. When you are ready to transfer to the serving plate, place the plate over the top of the cake and invert it to transfer.