Preheat oven to 350°F. Grease a 13x9-inch baking pan and line with parchment paper. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, mix together the crust ingredients on low speed until no large chunks of butter remain and the mixture resembles coarse sand.

Use your hands or the bottom of a measuring up to firmly press the mixture into the bottom of the prepared pan. Bake for 12 minutes, or until the edges start to turn golden brown and the center is just set. Set aside.

Make the filling: In a large bowl, toss together the sliced apples with the lemon juice and vanilla bean paste. Add the flour, sugar, and apple pie spice and toss to thoroughly coat the apples. Set aside.

Make the topping: Add the flour, oats, brown sugar, baking powder, apple pie spice, and salt to the stand mixer bowl (no need to wash it between making the crust and the topping). Mix for about 30 seconds with the paddle attachment, just until mixed. Add the butter and mix for 1-2 minutes on low speed, until there are no more dry ingredients visible and the mixture forms clumps.

If you’re going for the caramel layer, unwrap the caramels and use kitchen scissors sprayed with nonstick cooking spray to cut each caramel into 4 pieces. Scatter these pieces as evenly as you can onto the crust layer.

Sprinkle just under half of the topping evenly across the crust. Spread the apple filling in an even layer across the top, then finish with the rest of the topping.

Bake for 40-45 minutes, until the topping is golden brown and the apples have softened. Let cool before slicing.

If desired, drizzle with salted caramel sauce and top with a scoop of ice cream.