Preheat your oven to 350°F (175°C) and prepare three 9-inch round cake pans by greasing and dusting them with flour.

Cream together 1 cup of softened butter and 2 cups of granulated sugar using an electric mixer on medium speed for 3-5 minutes.

Add 4 large eggs one at a time, then mix in 1 cup of buttermilk and 1 tablespoon of vanilla extract until combined.

In another bowl, whisk together 3 cups of flour, 1 tablespoon of baking powder, 1 teaspoon of baking soda, and 0.5 teaspoon of salt. Gradually add to wet ingredients.

Fold in 2 cups of diced Granny Smith apples into the batter.

Divide the batter into prepared pans and bake for 25-30 minutes. Cool in pans for 10 minutes before transferring to wire racks.

To prepare the caramel sauce, melt 1 cup of sugar over medium heat until amber. Stir in 0.25 cup of butter, then whisk in 0.5 cup of heavy cream, 1 teaspoon of vanilla, and a pinch of salt.

Beat 1 cup of softened butter until creamy for the frosting. Gradually add 4 cups of powdered sugar, followed by 0.25 cup of heavy cream, 1 teaspoon of vanilla, and a pinch of salt.

Assemble the cake by layering with frosting and caramel between the layers.

Frost the top and sides of the cake and garnish with remaining caramel sauce and extra diced apples.