Step 1: Preheat your oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving an overhang on the sides.
Step 2: For the crust, combine 1 1/2 cups flour, 1/2 cup granulated sugar, and salt in a large bowl.
Step 3: Add the cold, cubed butter to the flour mixture. Cut the butter into the flour using a pastry blender, your fingertips, or a food processor until it resembles coarse crumbs.
Step 4: Press the crumb mixture evenly and firmly into the bottom of the prepared baking pan. Use the bottom of a flat-bottomed glass to compact it well.
Step 5: Bake the crust for 18-20 minutes, or until lightly golden brown around the edges. While baking, prepare the lemon filling.
Step 6: In a separate medium bowl, whisk together the 4 large eggs until well combined.
Step 7: Gradually add 1 1/2 cups granulated sugar to the eggs, whisking constantly until the mixture is pale yellow and slightly thickened.
Step 8: Whisk in the fresh lemon juice, lemon zest, and the remaining 2 tablespoons of all-purpose flour until smooth.
Step 9: Once the baked crust is out of the oven, immediately pour the lemon filling evenly over the hot crust.
Step 10: Return the pan to the oven and bake for an additional 20-25 minutes, or until the center is just set and has a slight jiggle. The edges might be lightly golden.
Step 11: Remove from the oven and let the lemon bars cool completely on a wire rack at room temperature. This can take 2-3 hours.
Step 12: Once completely cooled, refrigerate the bars for at least 1-2 hours before cutting. Chilling makes them much easier to slice neatly.
Step 13: Using the parchment paper overhang, lift the entire slab of lemon bars out of the pan and transfer it to a cutting board.
Step 14: Dust generously with powdered sugar before slicing into squares. For cleaner cuts, wipe your knife with a damp cloth between each slice.
Step 15: Store leftover lemon bars in an airtight container in the refrigerator for up to 5 days.