Preheat oven to 350°F (175°C). Line a 9x13-inch glass baking dish with parchment paper, leaving overhang on the sides. Set aside.

In a mixing bowl, combine butter, sugar, and flour. Beat with a hand mixer until crumbly. Press firmly and evenly into the prepared pan.

Bake the crust for 20–22 minutes, until the edges are lightly golden. Remove from the oven and poke small holes across the surface with a fork (don't poke all the way through).

In a large bowl, whisk together sugar and flour. In a separate bowl, whisk eggs and lemon juice. Gradually stir the egg mixture into the sugar-flour mixture until smooth.

Pour the lemon filling over the warm crust.

Bake at 350°F for 25–30 minutes, until the center is set and doesn't jiggle.

Cool completely at room temperature (about 2 hours), then refrigerate for at least 2 more hours.

Lift bars from the pan using the parchment overhang. Dust with powdered sugar, cut into squares, and serve cold.