Preheat the oven to 350°F.

Line a 9x13-inch baking dish with parchment paper or foil, leaving an overhang on the sides.

In a medium bowl, mix the softened butter and sugar until creamy and smooth.

Add the flour and salt, and stir until the mixture becomes crumbly.

Press the crust mixture evenly into the prepared pan, making sure to reach all corners.

Bake the crust for 18 to 20 minutes, or until the edges are lightly golden.

Remove from the oven and let it cool slightly while preparing the filling.

In a clean bowl, whisk together the sugar and flour until combined.

Add the eggs and lemon juice, and whisk until the mixture is completely smooth.

Pour the lemon mixture over the warm, partially baked crust.

Return the pan to the oven and bake for 20 to 25 minutes, or until the filling is set and no longer jiggles.

Remove from the oven and allow the lemon bars to cool completely in the pan.

Once cooled, lift the bars out using the parchment overhang and transfer to a cutting board.

Dust the top with powdered sugar, if using.

Slice into 16 even squares and serve chilled or at room temperature.

Store leftovers in an airtight container in the refrigerator for up to 5 days.