This Caramel Apple Cake is a showstopper and the perfect cake for any occasion and the upcoming holiday season. Soft apple cake layers filled with apple cinnamon filling, frosted with caramel buttercream and topped with caramel sauce.
Caramel sauce: In a small saucepan, combine butter, brown sugar, heavy cream, salt, and honey and bring over medium heat to a boil. Cook for about 10 minutes until it has thickened up and coats the back of a spoon but is still liquid. Whisk continuously. Test the caramel down the side of the saucepan to get the right thickness. The caramel should be thick enough to drip and doesn't run down like water. But don't cook it too long that it is not too stiff to pour it on top of the cake when it is cool. The caramel will thicken as it cools. Remove saucepan from the heat. With a heatproof cup scoop out 1/2 cup of caramel sauce and transfer to a small bowl and let cool to room temperature (you need this for the buttercream later). Cover saucepan and let stand overnight at room temperature until your cake is ready for decoration. Read the blog post above about cooking caramel. Also, watch 90 sec. video.
Apple filling: Place all ingredients in a large saucepan and bring over medium heat to a boil. Cook for 8-10 minutes until the apples are soft. Stir constantly. Remove from heat and let cool to room temperature.
Preheat oven to 350°F / 175°C. Line the bottom and the sides of two 8" (20cm) baking pans with parchment paper. Set aside.
Apple cake: In a medium bowl combine flour, baking powder, cinnamon, and salt and stir to combine. Set aside. In a large mixing bowl with a stand or handheld mixer fitted with a whisk or paddle attachment, beat oil and sugar until well combined for about 2 minutes. Add applesauce and vanilla* and stir until combined. Add eggs and mix until fully incorporated. Stir in dry ingredients just until combined. Divide batter into the two prepared baking pans equally. Bake for 18-22 minutes or until a toothpick in the center comes out clean. Don't overbake. Let cool to room temperature.
Caramel buttercream frosting: In a large mixing bowl beat butter on medium speed until super creamy, about 2-3 minutes. Sift in powdered sugar and whisk until the sugar is dissolved. Stir in vanilla*. Add 1/2 cup cooled caramel sauce and stir until super creamy. If the buttercream is too firm, you can add 1 tbsp heavy cream to lighten it up. If it is too creamy to spread on the cake, add more powdered sugar to thicken it up. The buttercream should be creamy and fluffy but firm enough to spread.
Assemble the cake: Cut a thin layer off the tops of your cakes to create a flat surface. Then cut each cake in half horizontally. Place one cake layer on a cake stand, turner or serving plate. Spread 1/4 of the buttercream over the cake. The buttercream should be higher around the edges that it holds the apple filling inside the cake (watch the video for better understanding). Layer with 1/3 of the apple filling without any liquid (where the buttercream is lower). Repeat two more times. Place last cake layer on top and lightly frost the outside and the sides of the cake with the remaining frosting. Chill at least 3 hours in the fridge or overnight.
Heat caramel on low heat that it is lukewarm. Transfer to a multi-cup glass measuring cup. Let stand a few minutes until the caramel is hand warm. The caramel should be thick but still pourable. While the caramel stands, push stick(s) into the tops of the apple(s). Then dip apple(s) into caramel and place on a parchment paper layered baking sheet. Sprinkle apple(s) with nuts if desired. Slowly pour the remaining caramel on top of the cake. Start in the center and move the cup like a spiral outwards to the edges of the cake and let drip off the sides. Watch 90 seconds video for better understanding. Place apple(s) on top of the cake and sprinkle with nuts if desired. Place cake in the fridge for 15 minutes that the caramel gets firm if needed. Store leftovers in an airtight container in the fridge up to 3 days. Leftover slices are best eaten when you let them sit at room temperature for 15 minutes before serving.
*First, cut off the straight end of the vanilla bean. Then place the tip of your knife below the curled end and cut the vanilla bean through the middle of the bean lengthwise with a sharp knife. Although you don't need to cut it all the way through, it's ok when you do so. Then open the vanilla bean and scrape out the flavorful seeds with the back of your knife. Just use the seeds.