Caramel Apple Cake

Preheat oven to 350F; butter and flour 2 (9-inch) round baking pans.For the cake, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg in a medium bowl and set aside. In a large bowl, whisk together the sugar and eggs until light and fluffy, then whisk in the oil, milk, and vanilla. Gradually stir the dry ingredients into the wet, and then fold in the shredded apple, being careful not to over-mix.Divide the batter between the 2 prepared pans, and bake until golden on top and a toothpick inserted inside comes out clean or with just a couple crumbs, about 20 to 25 minutes. Cool completely before assembling.For the homemade caramel sauce, combine the cream and vanilla in a small bowl and set aside.

Add the sugar and water to a medium-sized thick-bottomed pot; turn the heat on medium-high and cook until the sugar is caramelized and amber in color (see this post for more explanation); you can give the pot a swirl to help the water and sugar dissolve, but do not stir until about of the sugar is melted. From that point on, gently stir constantly with a wooden spoon.Once the sugar turns amber-colored, carefully add the butter and salt, and stir to combine. Once the butter is melted, turn off the heat and carefully pour in the cream mixture, stirring until smooth. Cool completely before using or storing.For the frosting, use a handheld electric beater to cream together the butter, shortening, vanilla, and cinnamon in a large bowl. Alternate between beating in the powdered sugar and milk until all the powdered sugar is added and the frosting is smooth and creamy.Measure out 3 tablespoons from the cup of caramel sauce that you'll need for this recipe; transfer it to a small bowl and reserve it for drizzling on top of the cake once its frosted.To assemble the cake, turn 1 cake round out onto a cake stand.

Spread on the remaining caramel sauce from the cup that you'll need for this cake (other than the reserved 3 tablespoons), leaving a border of about -inch all around.Refrigerate 1 hour or until fully chilled, then carefully place the other cake round on top. Frost the top and sides with Vanilla-Cinnamon Frosting, and drizzle the reserved 3 tablespoons of caramel sauce decoratively on top.Chill the cake 1 hour before cutting and serving; wrap any leftover cake in plastic wrap and store in the fridge.