Heat oven to 325 degrees Fahrenheit.
Spread bread cubes evenly over 2 rimmed baking sheets and toast for 10 to 15 minutes, stirring or tossing every 5 min or so until dry. Meanwhile combine the brown sugar and 1 tbsp of granulated sugar in a small bowl and set aside. Make sure apples are peeled and diced, set aside.
Once bread cubes are toasted allow to cool. Reserve 2 cups of bread cubes and set aside.
Whisk eggs, 3/4 cup of sugar, vanilla and salt in a large bowl until combined.
Whisk in milk and cream until combined to make a custard mix.
Add in 8 cups of toasted bread cubes and diced apples to the custard mix. Press bread cubes down to soak in the mixture then pour mixture into a 9X13 baking dish and let soak for 30 minutes. Press bread cubes into the mixture occasionally.
Spread the reserved 2 cups of toasted bread cubes over the top of the custard mix in the baking dish. Gently press down into the custard. Brush the melted butter over the unsoaked cubes. Bake for 40 min at 325 degrees Fahrenheit.
Remove from oven and top with salted caramel sauce and sprinkle 1 tsp of sea salt over the dish. Allow to cool before serving.
Serve with additional salted caramel sauce if desired.