• Preheat your oven to 375°F and line a 13×9-inch baking dish with parchment paper, leaving some overhang on the edges for easy lifting later.

Prepare the apples:

• In a large bowl, toss the diced apples with brown sugar, cornstarch, cinnamon, and lemon juice. Let the mixture sit for about 5 minutes to release the juices.
• Melt 6 tablespoons of butter in a large sauté pan over medium heat. Add the apples, including their juices, and cook for about 10 minutes, or until the apples are fork-tender. Let them cool slightly before using.

Make the crust and topping:

• In a stand mixer fitted with the paddle attachment, combine the flour, sugar, baking powder, and salt. While the mixer is running, add the cold butter one tablespoon at a time until the mixture forms fine crumbs. Mix in the egg until the dough comes together in large crumbs.
• Press two-thirds of the dough evenly into the bottom of the prepared baking dish to create the crust. Spread the cooked apples evenly on top, then crumble the remaining dough over the apples for the topping.
• Bake for 25 - 30 minutes, or until the topping is golden brown and the apple filling is bubbling slightly in the center.
• Let the bars cool completely in the pan. Use the parchment paper overhang to lift them out for easy cutting and serving. Store any leftovers covered at room temperature. Enjoy!