TIP: Only make these bars in a dish made from glass or other nonreactive material. Don’t use an aluminum or other metal pan because the lemon will react to it.
Nonstick baking spray or softened butter, for the pan
2 cups all-purpose flour
1/2 pound (2 sticks) salted butter, melted
1/2 cup powdered sugar, plus more for garnish
1/4 teaspoon sea salt
2 cups granulated sugar
4 eggs, slightly beaten
5 tablespoons fresh lemon juice (from about 2 lemons)
Position a baking rack in the middle of the oven and preheat the oven to 350°F. Spray a 9 x 13-inch glass (see Cook’s Note) baking dish with baking spray or grease with butter.
In a medium bowl, combine the flour, melted butter, powdered sugar, and salt. Use a fork to stir gently until just barely combined; mixing as little as possible will result in a flakier crust. Use your fingers to press the mixture into the prepared pan.
Bake until the edges of the crust are very lightly browned, about 20 minutes.
Meanwhile, in a medium bowl, whisk together the granulated sugar, eggs, and lemon juice until well blended.
When the crust is done, pour the lemon mixture over the hot crust, return to the oven, and bake for 15 minutes. Gently tent a piece of foil on top to prevent over browning and bake until the top is lightly browned and the center is set when the pan is gently nudged, about 15 minutes.
Remove from the oven and dust the top with powdered sugar. Let cool completely on a rack in the pan, then cut into 15 bars or 30 squares. The bars are much easier to cut when completely cool.
Store in an airtight container at room temperature for up to 1 week. For longer storage, wrap in plastic or in zip-top bags and freeze for up to 1 month..