Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a mixing bowl, whisk together the all-purpose flour and salt until evenly combined.

Using an electric mixer, cream together the unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes.

Gradually add the flour mixture to the butter-sugar blend, mixing on low speed until a crumbly dough forms.

Press approximately two-thirds of the dough evenly into the bottom of the prepared baking dish.

In a large bowl, toss the sliced Granny Smith apples with sugar, cinnamon, nutmeg, lemon juice, and cornstarch until well coated.

Spread the apple mixture evenly over the prepared crust in the baking dish.

Crumble the remaining dough evenly over the top of the apple filling.

Place the baking dish in the preheated oven and bake for 40-45 minutes, or until golden brown and bubbly.

Once baked, remove from the oven and allow to cool for at least 30 minutes before slicing.

For an extra treat, drizzle with caramel sauce before serving if desired.