Preheat oven to 350°F (175°C) and grease a muffin tin.
In a bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition.
Gradually add the flour, baking powder, and salt, mixing until just combined. Fold in the chopped apples.
Spoon the batter into the prepared muffin tin, filling each cup halfway. Add a tablespoon of caramel sauce to the center of each and top with additional batter.
Bake for 20-25 minutes until golden brown and a toothpick inserted into the cake comes out clean.
Notes
Let the cake cups cool in the pan for a few minutes before transferring to a wire rack to cool completely.