Preheat the oven to 350°F and line an 8x8 inch pan with parchment paper, leaving overhang on two sides.

Mix 1 1/4 cups flour, 1/4 cup powdered sugar, and 1/4 teaspoon salt; cut in the cold butter until the mixture clumps when pressed.

Press the mixture into the bottom of the pan evenly and bake for 18 to 20 minutes, until the edges are light golden.

Meanwhile, whisk the eggs, granulated sugar, 1/3 cup flour, lemon juice, and zest until smooth.

Pour the lemon filling over the hot crust immediately after baking.

Bake for 20 to 22 minutes, until the center is set and jiggles only slightly in the middle, like firm gelatin, not liquid.

Cool completely in the pan on a rack, about 1 hour 30 minutes, then refrigerate for 30 minutes for cleaner cuts.

Lift out by the parchment overhang and cut into 16 squares, wiping the knife between cuts.

Dust with powdered sugar just before packaging.

Layer the bars in a bakery box between sheets of parchment so the sugar dusting and soft top do not stick to the lid.