• Preheat the oven to 350°F. Line a 9×13-inch baking dish with parchment paper. Spray the parchment paper around the edges of the pan with nonstick spray to keep the lemon filling from sticking. Set aside.

Make the shortbread crust.

• In a medium bowl, whisk together the flour and confectioners’ sugar.
  2 ½ cups all-purpose flour, ⅝ cup confectioners' sugar
• Add the cubes of softened butter and cut the butter into the flour mixture using a pastry cutter until a slightly crumbly dough forms and begins to clump together.
  1 ¼ cup unsalted butter
• Spread the dough into the prepared pan and gently press the dough into the bottom of the pan to create a solid crust. Make sure the crust reaches all the way into the edges and corners of the pan and that there are no holes in the crust.
• Bake the crust for 20-25 minutes, just until golden. Remove the crust from the oven and reduce the oven temperature to 300°F. Let the crust cool slightly while you prepare the lemon filling.

Make the lemon filling.

• In a large bowl, gently beat the eggs. Add the sugar, flour, baking powder, and lemon juice and beat well until smooth and slightly thickened.
  4 large eggs, 2 cups granulated sugar, ¼ cup all-purpose flour, 1 teaspoon baking powder, 6 Tablespoons fresh lemon juice
• Pour the mixture over the still-warm crust.

Bake the lemon bars.

• Return the pan to the 300°F oven and bake for 30 minutes or until the top is lightly golden and the filling does not wiggle when you jiggle the pan. Place the pan on a cooling rack and let the bars cool completely.
• Once cooled, lift up on the edges of the parchment paper to remove the bars from the pan. Sprinkle the bars generously and evenly with confectioners sugar using a sifter or fine mesh sieve. Then gently slice the bars into 24 squares.
  2 Tablespoons confectioners' sugar