Begin by peeling, coring, and slicing three medium-sized apples into thin wedges, ensuring they’re about 1/4 inch thick. Preheat your oven to 350°F (175°C).

Melt 1/2 cup of unsalted butter in a medium saucepan, then mix in 1 cup of brown sugar and 1 teaspoon of ground cinnamon until bubbly and well combined, about 3-5 minutes. Pour this warm caramel mixture into a greased 9-inch round cake pan.

Layer the sliced apples atop the caramel in the cake pan, arranging them in a circular pattern.

In a large mixing bowl, whisk together 1 1/2 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, and 1/2 teaspoon of salt. In another bowl, cream together 1 cup of granulated sugar and 2 large eggs until light and fluffy. Add 1 teaspoon of vanilla extract and 1/2 cup of milk, mixing until just combined before folding in the dry ingredients.

Pour the cake batter evenly over the arranged apples in the pan, smoothing the top with a spatula. Bake for 40 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for about 10 minutes, then run a knife around the edges to loosen it. Carefully invert the cake onto a serving plate.