Step 1: Preheat Oven and Prepare Pan.

Preheat the oven to 350°F (175°C).

Grease a 13-by-9-inch pan with butter. (Use an 8-by-10-inch pan if you’d like the layers to be a little thicker.)

Step 2: Make the Crust.

In a large bowl, stir together the flour, sugar, and salt.

Add the cold, cubed butter.

Use a pastry cutter (or two knives) to cut the butter into the flour mixture until it resembles fine crumbs.

Press the mixture evenly into the prepared pan.

Bake until golden around the edges, about 20 minutes.

Step 3: Make the Filling.

While the crust is baking, prepare the filling.

In a medium bowl, stir together the sugar and flour.

Crack in the eggs. Whisk to combine until smooth.

Add the lemon zest and juice. Mix until combined.

Step 4: Bake the Lemon Bars.

Pour the lemon filling over the warm crust.

Bake until the filling is set, about 20 minutes. The center should be just barely jiggly.

Step 5: Cool and Finish.

Allow the lemon bars to cool completely in the refrigerator for a minimum of 2 hours. This allows the filling to set completely.

Once chilled, sift powdered sugar over the top.

Cut into squares and serve.