For the Cake
Preheat the oven to 350 degrees F and spray your bundt pan with cooking spray.
In a medium bowl, sift together the flour, cinnamon, baking powder, baking soda and salt.
In a separate bowl, combine the butter, brown sugar, and eggs. Gently whisk until smooth.
Slowly whisk in the dry ingredients until they're combined. Don't beat or mix too much - you just want the dry ingredients to incorporate into the wet.
Use a spoon to turn the apples into the batter and pour into the bundt pan.
Bake for 1 hour or until a toothpick comes out clean. Allow to cool in the pan for 20 minutes and then turn out onto a serving dish.
While the cake is baking start preparing your caramel.
For the Caramel
In a small sauce pan heat the heavy cream over low heat.
Add the Sugar and water to a heavy sauce pan. Bring to a boil over medium high heat without stirring.
Allow the sugar mixture to continue boiling until it reaches 360 degrees F or a deep amber color.
Once the caramel reaches the desired color/temperature remove it from the heat and slowly add the sliced butter. Be careful as this will most likely sizzle and splatter.
Pour in the heavy cream and allow it to settle (stop sizzling/bubbling.)
Whisk for 10 - 15 minutes until the caramel begins to thicken and becomes smooth.
Let it cool for 15 - 20 minutes before topping your cake.