Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking pan and line it with parchment paper, leaving an overhang for easy removal.

In a medium bowl, whisk together 2 cups sifted flour, powdered sugar, and salt. Cut in cold cubed butter with a pastry cutter until the mixture resembles coarse crumbs.

Press the crust evenly into the bottom of the prepared pan. Bake for 18–20 minutes, or until the edges just begin to turn golden.

Meanwhile, whisk together granulated sugar, eggs, lemon zest, lemon juice, ¼ cup flour, baking powder, and a pinch of salt until smooth and frothy.

Pour the lemon mixture over the hot crust and return to the oven. Bake for an additional 20–25 minutes, or until the center is set and no longer jiggly.

Let the bars cool completely at room temperature, then refrigerate for at least 1 hour to firm up.

Use the parchment paper overhang to lift the bars out of the pan. Dust with powdered sugar if desired, then cut into 24 even squares.