Preheat the oven to 350°F. Lightly grease an 8 x 8-inch pan with cooking spray.
In the bowl of a food processor (or in a medium mixing bowl if not using a food processor), lightly pulse the all-purpose flour, whole-wheat pastry flour, powdered sugar, 1/4 teaspoon of lemon zest, and salt. Add butter pieces and pulse just until the mixture is crumbly and resembles coarse cornmeal. (If not using a food processor, cut butter pieces into the dry ingredients with a fork or pastry blender.) The mixture will feel dry to the touch.
Press the mixture into the bottom of the prepared pan.
Bake 20 to 22 minutes, until lightly browned. Set aside to cool for at least 15 minutes.
Meanwhile, in the bowl of a standing mixer fitted with the paddle attachment (or a large mixing bowl), beat together the cream cheese, Greek yogurt, and granulated sugar until smooth.
Add the egg and beat just until blended.
Mix in the fresh lemon juice, cornstarch, vanilla, and remaining 1/4 teaspoon of lemon zest. Beat well.
Pour the cream cheese mixture over the crust, spreading it to the edges. Bake for 28 to 32 minutes, or until the cheesecake appears set on top and only jiggles slightly when you wiggle the pan. Let cool on a wire rack for 1 hour then cover and chill for 4 to 8 hours. Cut into bars and garnish with whipped cream, if desired.
Notes
TO STORE: Keep leftover lemon cream cheese bars in an airtight container in the refrigerator for up to 2 days.
TO FREEZE: Wrap tightly in a double layer of plastic, and freeze for up to 1 month. Let thaw in the refrigerator, then serve.
RECIPE VARIATION: For a fun fruity twist, spread a thin layer of your favorite fruit preserves over the cooled crust before pouring in the creamy lemon cheesecake filling. Strawberry, raspberry, or blueberry preserves are some of my favorites that pair perfectly with lemon.