This upside-down apple cinnamon cake is a unique and delicious twist on the classic apple cake. It's made with sliced apples and a caramel sauce that's poured on top of the cake batter before baking. The cake is moist, tender, and packed with apple and cinnamon flavors. To make this cake, you'll need flour, sugar, baking powder, salt, cinnamon, eggs, oil, vanilla extract, sliced apples, and brown sugar. Mix the dry ingredients in one bowl and the wet ingredients in another. Arrange the sliced apples on the bottom of a greased baking pan and pour the caramel sauce on top. Pour the cake batter over the apples and bake for 35-40 minutes. Let the cake cool for a few minutes before flipping it over onto a serving plate.