All-purpose flour, for pan
1 box spice cake mix, plus ingredients called for on box
5 Granny Smith apples, finely chopped (peeled if desired)
1/4 c. sugar
1/4 c. brown sugar
1 tbsp. cinnamon, plus more for dusting
1 tsp. ground nutmeg
1 tbsp. cornstarch
Juice of 1/2 lemon
1 1/4 c. jarred caramel, plus more for drizzling
For the frosting
16 oz. cream cheese, softened
8 tbsp. butter, softened
2 1/4 c. powdered sugar
1 1/2 tsp. pure vanilla extract
Butter and flour a 9"-x-13" baking pan or dish. Prepare spice cake according to package directions and pour into prepared pan. Bake according to package directions, then let cool 20 minutes. While cake cools, prepare apple layer: In a large skillet over medium heat, melt butter. Add apples and cook until soft, stirring occasionally, 8 minutes. Add sugars, cinnamon, and nutmeg and stir until combined. Add cornstarch and lemon juice and stir until combined, then remove from heat. Poke holes all over cake and pour over caramel, letting caramel seep into holes. Spread apples on top, creating one even layer. Make frosting: In a large bowl using a hand mixer or in the bowl of a stand mixer using the whisk attachment, beat cream cheese and butter until light and fluffy. Add powdered sugar and vanilla and beat until combined. Spread frosting over apple layer using an offset spatula or knife. Drizzle cake with more caramel and dust with cinnamon.