01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper, allowing overhang on the sides for easy removal later.
02 - In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. Mix in the flour and salt until a soft dough forms. Press the dough evenly into the bottom of the prepared pan.
03 - Bake the crust for 18-20 minutes, until lightly golden around the edges. Remove from oven and set aside.
04 - In a medium bowl, whisk together the 1 1/2 cups sugar and 1/4 cup flour. Add the eggs, lemon juice, and lemon zest; whisk until smooth and fully combined.
05 - Pour the lemon filling directly over the hot crust. Return to the oven and bake for an additional 18-20 minutes, until the center is just set and no longer wobbly.
06 - Remove from the oven and let cool completely in the pan on a wire rack for approximately 1 hour.
07 - Whisk together the powdered sugar, 2-3 tablespoons lemon juice, and lemon zest until smooth and pourable. Adjust consistency with more or less juice as desired. Spread evenly over the cooled bars. Let glaze set for 20-30 minutes.
08 - Lift the bars from the pan using the parchment overhang. Cut into 16 squares with a sharp knife. Serve chilled or at room temperature.