In a large bowl, toss the apples with the lemon juice.
In a large skillet, melt the butter over medium heat. Add the apples, sugar, cinnamon and salt. Cook, stirring occasionally until the apples are tender, about 10-12 minutes. Set aside to cool.
In a medium bowl, whisk together the flour, brown sugar, sugar, cinnamon and salt. Work the cold butter into the flour mixture with a pastry blender or with your fingertips until it looks like wet sand. Press together to form 1/2-inch chunks. Set aside in the refrigerator until ready to use.
In a small saucepan over medium heat, melt the caramel candies and heavy cream together, stirring until smooth.
Preheat the oven to 350ºF. (180ºC). Line an 8-inch square baking pan* with parchment paper.
In a medium bowl, whisk together the flour, powdered sugar, baking powder and salt.
In a large bowl, beat the butter, with an electric mixer at medium speed, until smooth. Add the flour mixture and beat just until the dough comes together.
Press the dough into the prepared baking pan. Bake until the surface looks evenly light golden brown, about 20-22 minutes. Remove from the oven. Top with the cooked apples. Drizzle with caramel sauce. Top with the crumble topping. Return the pan to the oven and continue baking until the topping looks golden brown and the filling starts to bubble, about 25-28 minutes.
Let cool completely in the pan. Sprinkle with powdered sugar.