First, let's prepare the Salted Caramel Sauce. In a large saucepan, heat the granulated white sugar over medium-low heat until it melts and turns golden in color. This usually takes around 20 minutes.

Once the sugar has melted, quickly add the softened butter and stir until incorporated. Then, pour in the heavy cream and continue stirring until well combined.

Add the vanilla extract and salt, stirring to combine. Let the caramel sauce simmer for 2-3 minutes before removing it from the heat to cool completely.

Preheat your oven to 375 degrees Fahrenheit and prepare a 9x9 metal baking pan by greasing it and lining the bottom and two sides with parchment paper.

For the Shortbread Crust, cream together the softened butter, brown sugar, granulated sugar, and vanilla extract until light and fluffy. Then, mix in the flour and salt until crumbly, and press the dough into the prepared pan.

Bake the crust for 12-15 minutes until lightly golden brown, then let it cool.

Meanwhile, prepare the Streusel Topping by creaming together the butter and brown sugar, then adding the flour, salt, and cinnamon until large crumbs form. Place the streusel in the freezer while you work on the filling.

For the Apple Filling, combine the diced apples, salted caramel sauce, and spices in a large saucepan. Cook over medium heat, covered, for 16-20 minutes until the apples are tender. Let them cool for 10 minutes.

Assemble the bars by spreading the cooked apple mixture over the cooled crust, then sprinkle the streusel on top.

Bake the bars for 30-35 minutes until lightly golden brown, then let them cool completely in the pan before cutting into 16 bars and drizzling with caramel sauce.