Prepare the Cake

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans.
2. Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
3. Cream Butter and Sugars: In a large bowl, beat the softened butter with the granulated sugar and brown sugar until light and fluffy.
4. Add Eggs and Vanilla: Beat in the eggs, one at a time, followed by the vanilla extract.
5. Alternate Wet and Dry Ingredients: Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk. Mix just until combined.
6. Fold in Apples: Gently fold in the chopped apples.
7. Divide and Bake: Divide the batter evenly between the prepared cake pans. Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.

Cool the Cakes

1. Cool in Pans: Allow the cakes to cool in the pans for 10 minutes.
2. Transfer to Wire Racks: Turn the cakes out onto wire racks to cool completely before frosting.

Make the Frosting

1. Beat the Butter: In a mixing bowl, beat the softened butter until creamy.
2. Add Powdered Sugar: Gradually add the powdered sugar, mixing well.
3. Incorporate Caramel and Cream: Beat in the salted caramel sauce, heavy cream, and vanilla extract until the frosting is smooth and fluffy.

Assemble the Cake

1. Layer the Cakes: Place one cake layer on a serving plate. Spread a generous layer of frosting on top.
2. Add Second Layer: Place the second cake layer on top. Frost the top and sides of the cake with the remaining frosting.
3. Decorate with Snickers and Caramel: Sprinkle chopped Snickers bars on top and drizzle with salted caramel sauce.
4. Optional: Sprinkle sea salt flakes over the caramel for extra flavor.