Make the apples – in a small skillet, melt the butter over medium heat, add the apples, brown sugar and salt and cook for a few minutes until the sugar has dissolved and the apples have softened a titch.  Remove the pan from the heat and leave the apples to cool to room temperature.  Preheat the oven to 350 and generously butter a 10-inch cast iron skillet.

Make the cake – using your electric mixer, cream together the butter and sugar for a few minutes until the mix is light and fluffy.  Add the eggs, one at a time, beating well in between additions and scraping down the sides as needed, then beat in the vanilla.

In a separate bowl, whisk together the 5 dry ingredients and then add all to the batter and mix until just incorporated.  Use a sturdy spatula to scrape the bowl well and then fold in the cooled apples and any liquid that has appeared.  Scrape the finished batter into your prepared skillet and bake for 35-40 minutes until the center has set and the cake is a lovely golden brown.  Leave the cake to cool completely in the skillet.

Make the frosting – do not start this step until the cake has cooled completely!  Using your electric mixer again, carefully cream together the butter and icing sugar for a few minutes until light and fluffy.  As the creaming is happening, put all of the caramels into a microwave safe bowl and heat in 20 to 30 second increments until the caramels are just warm and melted.  The caramels will cool quickly so make sure you’ve timed them to finish melting as the creaming is also done.

Add the barely warm fluid caramels to the butter and icing sugar and mix on medium speed until all is well combined.  It may have an odd texture at this point, but as soon as you add the cream and vanilla and mix again, it will all smooth out perfectly.  The frosting should be smooth, but also very soft.

Scrape the frosting onto the cooled cake and smooth out into an even (thick!) layer.  Sprinkle with some flaky salt right before you serve it.