- In a medium-sized sauce pan stir together 1/4 cup cold water and granulated sugar until combined. 
- Set over medium-high heat on the stove top and cook 9 -11 minutes without stirring until mixture is a deep amber color. 
- Start checking closely at the 8 minute mark. 
- Meanwhile, warm heavy cream and butter together with sea salt in a small sauce pan over medium heat. (Absolutely do not boil.) 
- When sugar and water mixture is a deep amber color, slowly whisk in the warm cream and butter mixture. 
- Whisk over the heat until it's smooth a minute or two, then remove from the heat. 
- Salted caramel sauce will thicken up as it cools. 
- When sauce is still warm, spoon over apple cake and cascade down the sides. 
- (Re-heating the caramel sauce will thin it.)