Preheat the oven to 350°F (175°C) and grease four 8-inch round cake pans. Set the prepared pans aside.

In a medium-sized bowl, whisk together the flour, baking powder, salt, cinnamon, nutmeg, cloves, and ginger until well combined. Set the dry ingredients aside.

In a large mixing bowl, beat together the softened butter, vegetable oil, applesauce, and granulated sugar until the mixture is smooth and creamy. Add the eggs one at a time, followed by the vanilla extract, and mix until fully incorporated.

Gradually add the dry ingredients to the wet mixture, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined, then gently fold in the chopped apples.

Evenly divide the batter among the four prepared cake pans.

Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center of each cake comes out clean.

Allow the cakes to cool completely in the pans before transferring them to a wire rack. Meanwhile, prepare the buttercream.

In a large mixing bowl, beat the softened butter, vanilla extract, caramel sauce, and cinnamon until the mixture is light and creamy.

Gradually add the powdered sugar in batches, beating well after each addition, until the buttercream is smooth and fluffy.

Level the tops of the cooled cakes with a serrated knife to create an even surface.

Place the first cake layer on a serving plate or cake stand, then spread a layer of buttercream evenly on top. Repeat this process with the remaining cake layers.

Apply a thin crumb coat of buttercream to the top and sides of the stacked cake using a large icing spatula. Smooth it out evenly, then chill the cake in the freezer for about 15 minutes to set the crumb coat.

Once the crumb coat is firm, frost the entire cake with the remaining buttercream, smoothing it as desired.

For decoration, drizzle caramel sauce over the edges to create a drip effect and garnish with fresh apple slices if desired.

Slice, serve, and enjoy your decadent Caramel Apple Spice Cake!