1. Prepare three 8 inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C) .
2. In a large mixing bowl, cream the butter and sugar together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
3. Add sour cream and vanilla extract and mix until well combined.
4. Add egg whites in two batches, mixing until well combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Combine dry ingredients in a separate bowl, then combine the apple butter and milk in a small measuring cup.
6. Add half of the dry ingredients to the batter and mix until well combined. Add the apple butter mixture and mix until well combined. Add remaining dry ingredients and mix until well combined. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Stir in the pecans.
7. Divide the batter evenly between the cakes pans and bake for about 22-24 minutes, or until a toothpick comes out with a few crumbs.
8. Remove the cakes from the oven and allow to cool for about 3-5 minutes, then remove to cooling racks to cool completely.

WHILE CAKES BAKE AND COOL, MAKE THE CARAMEL SAUCE AND FROSTING:

9. Pour sugar into an even layer in a large saucepan.
10. Heat on medium-high heat, whisking the sugar until melted. The sugar will clump up first, but will eventually completely melt. This will take about 10 minutes.
11. Once the sugar has melted, stop whisking and allow to cook until the sugar has turned to a little darker amber color. You may notice a nutty aroma. The change in color will happen quickly, so don’t let it go too long or get too dark or it’ll burn. Remove caramel from the heat.
12. Add butter and whisk until combined. The mixture will bubble up, but keep whisking until all the butter has melted and combined.
13. Slowly pour the heavy cream into the caramel and whisk until incorporated.
14. Cool at least 10-15 minutes before using. See notes in above post about frosting and caramel consistency.
15. Set aside about 3/4 cup of caramel sauce for using on top of the cake later. Transfer remaining caramel sauce (about 1 1/4 cups) to a mixing bowl.
16. Slowly add powdered sugar and milk and mix until smooth. You can add more or less milk to get the right consistency for the icing.

TO PUT THE CAKE TOGETHER:

17. When the cakes are cool, remove the domes of the cakes with a large serrated knife so they are flat.
18. Place the first layer of cake on cake stand. Top with 1/2 of the caramel frosting and spread into an even layer.
19. Add second layer of cake and add remaining caramel frosting. Spread frosting into an even layer.
20. Top cake with the remaining cake layer.
21. To make the cinnamon apples, add everything to a large pan, toss together, and cook over medium heat until apples are tender.
22. Pile apples onto the top of the cake.
23. Use a spoon to drizzle the remaining caramel sauce down the sides of the cake. If the caramel sauce has cooled too much, warm it up in the microwave a bit.
24. Use the end of an offset spatula to spread additional caramel around the top edge of the cake, then drizzle a little more caramel sauce over the apples.
25. Finish off the cake with a sprinkle of chopped pecans.
26. Cake is best served when apples are fresh, but can be refrigerated until ready to serve if needed.