Preheat your oven to 375°F (190°C) and line a 9×13 inch baking pan with parchment paper.
In a large mixing bowl, combine melted butter, granulated sugar, vanilla extract, and salt until well mixed.
Add all-purpose flour to the mixture, stirring until crumbly. Press about two-thirds of this mixture evenly into the bottom of your prepared baking pan.
In another bowl, toss your thinly sliced apples with ground cinnamon and nutmeg. Spread this spiced apple mixture over the crust.
Drizzle salted caramel sauce generously over the layer of apples. Crumble the remaining flour mixture over the top.
Bake for about 40-45 minutes or until you see a golden brown topping and tender apples. Let them cool completely before cutting.