In a small saucepan, combine 90 g of granulated sugar and 1 tbsp of water and heat over medium-low until the sugar dissolves and turns golden.

Remove from heat and add 25 g of butter and a pinch of salt. Slowly whisk in 100 g of heavy cream. Set aside to cool.

Preheat your oven to 350°F (175°C) and grease two round cake pans.

In a bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and all spice.

In another bowl, mix granulated sugar, dark brown sugar, and grated apples.

Add vegetable oil, eggs, sour cream, and vanilla extract. Mix well.

Gradually add the dry ingredients to the wet ingredients until combined. Pour the batter evenly into the prepared pans.

Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat the butter until creamy. Gradually add powdered sugar and mix until smooth.

Pour in caramel and vanilla extract. Beat until fluffy.

Place one layer of the cake on a serving plate and spread a layer of caramel buttercream on top.

Add the second layer and frost the top and sides of the cake with the remaining buttercream.