• Preheat the oven to 375℉.

For the Crust

• Place the butter, sugar, brown sugar, and vanilla in the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed for 2 minutes, until light and creamy.
  2 Cups Unsalted Butter, ¾ Cup Granulated Sugar, ½ Cup Light Brown Sugar, 2 teaspoons Vanilla Extract
• Sift the flour, salt and cinnamon together and slowly add to the butter-sugar mixture, beating until combined.
  4 Cups All-Purpose Flour, 1 ¾ teaspoons Kosher Salt, 1 teaspoon Ground Cinnamon
• Scatter ⅔ of the dough in clumps in a 9×13-inch baking pan and press it lightly with floured hands on the bottom and ½ inch up the sides. Refrigerate for 20 minutes.
• Bake for 18 to 20 minutes, until the crust is golden brown, and set aside to cool.
• Reduce the oven to 350℉.

For the Filling

• Combine both types of apples and the lemon juice in a very large bowl.
  3 Granny Smith Apples, 3 Golden Delicious Apples, 2 Tablespoons Lemon Juice
• Add the sugar, cinnamon, and nutmeg and mix well.
  ¼ Cup Granulated Sugar, 1 teaspoon Ground Cinnamon, ⅛ teaspoon Ground Nutmeg
• Melt the butter in a large (10-inch-diameter) pot, add the apples, and simmer over medium to medium-low heat, stirring often, for 12 to 15 minutes, until the apples are tender and the liquid has mostly evaporated.
  4 Tablespoons Unsalted Butter
• Spread the apples evenly over the crust, leaving a ½-inch border.
• Pinch medium pieces of the remaining dough with your fingers and drop them evenly on top of the apples (they will not be covered).
• Bake for 25 to 30 minutes, until the topping is browned. Cool completely and cut into bars.
• Drizzle with caramel sauce if desired.
  Caramel Sauce