Set your oven to 350°F (175°C). Grease or line a 9×13-inch baking pan with parchment paper for easy removal.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), combine butter, flour, sugar, and salt. Beat on medium speed for 2–3 minutes, until the mixture looks crumbly but holds together when pressed.

Press the mixture evenly into the bottom of the prepared pan. Bake for 18–20 minutes, or until the edges are lightly golden. Remove from the oven but keep the oven on.

While the crust is cooling slightly, whisk together sugar, flour, eggs, lemon juice, and lemon zest in a large bowl until smooth and fully combined.

Pour the filling over the warm crust, spreading evenly. Bake for 18–22 minutes, or until the center is set and no longer jiggly.

Allow the bars to cool completely at room temperature, then refrigerate until firm (at least 2 hours). Before serving, dust with powdered sugar and slice into squares.