Apple Walnut Cheesecake Bars

1. Position a rack in the center of the oven and preheat the oven to 350°F. Line a 9×13-inch baking pan with parchment, leaving a 2-inch overhang on the ends. 

2. Make the crust and topping: In a food processor, finely grind ½ cup of the walnuts with the sugar. Add the flour, baking powder, and salt and pulse to blend. Add the butter and pulse until it’s the size of small peas. Transfer 1 generous cup of the mixture to a medium bowl and set aside. Add the egg to the mixture remaining in the food processor and pulse just until the dough begins to gather into large clumps.

3.With your fingertips, press the dough evenly into the bottom of the prepared pan. Using the tines of a fork, pierce the crust all over. Bake until the edges are lightly golden brown and the center looks dry, about 15 minutes. Cool the crust on a rack.

4. Meanwhile, work the reserved mixture with your fingertips until it becomes clumpy. Coarsely chop the remaining ½-cup walnuts and toss them into the mixture; set aside for the topping.

5. In a large mixing bowl, beat the cream cheese with an electric mixer on medium speed until smooth. Add the sugar and beat until blended scraping the bowl as needed. Add the egg and beat until combined, scraping the bowl as needed. Beat in the lemon zest, lemon juice, and salt.

6. Spread the apple slices evenly on the bottom crust and pour the cream cheese filling on top, gently spreading it with a rubber spatula to cover the apples. Crumble the reserved crumb mixture on top.  Bake until the topping is light golden brown, about 40 minutes.

7. Let the bars cool in the pan until warm, about 30 minutes. Remove from the pan by lifting the parchment ends and set on a cutting board.  Cut into 24 bars.