Step 1

Prepare the baking dish. Lightly coat a 7x11-inch or 8x8-inch baking dish with cooking spray or butter. Line the dish with a parchment paper sling, leaving an overhang of about 2 inches on two opposite sides; set aside.

Step 2

Make the crust. Place the flour, granulated sugar, powdered sugar, zest, and salt in the bowl of a food processor fitted with the blade attachment. Pulse 5 times to combine. Sprinkle with the butter cubes and pulse until the mixture looks like coarse crumbs.

Step 3

Press the crust in and chill while the oven heats. Pour the crust mixture into the prepared baking dish. Use the bottom of a measuring cup or your fingers to press the crumbs into an even layer. Refrigerate for 15 minutes. Meanwhile, arrange a rack in the middle of the oven and heat to 325°F.

Step 4

Parbake the crust. Bake the crust until light golden-brown, 25 to 30 minutes.

Step 5

Make the filling. Place the whole eggs, egg yolk, granulated sugar, powdered sugar, zest, and salt in a large bowl and whisk to combine. Whisk in the lemon juice, and then the flour, until combined.

Step 6

Pour the filling onto the warm crust. Remove the parbaked crust from the oven. Pour the lemon filling onto the warm crust.

Step 7

Bake and cool the lemon bars. Return the pan to the oven and bake until light brown around the edges, set in the middle, and the top appears relatively dry, 15 to 20 minutes. Cool completely on a wire rack, at least 1 hour, before serving.

Step 8

Dust with powdered sugar. Using a fine-mesh strainer, generously dust the bars with more powdered sugar.

Step 9

Cut the lemon bars. Grasping the parchment sling, lift the lemon bar slab out of the pan and onto a cutting board. Cut into 12 or 16 bars. Dust with more powdered sugar, if desired, before serving.