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 to easily lift out the bars later.
Step 2: In a large bowl, whisk together 1 1/2 cups all-purpose flour, 1/2 cup powdered sugar, and 1/4 teaspoon salt for the crust.
Step 3: Add the cold, cubed unsalted butter to the flour mixture. Using a pastry blender, your fingertips, or a food processor, cut the butter into the dry ingredients until the mixture resembles coarse crumbs.
Step 4: Press the crumb mixture evenly and firmly into the bottom of the prepared baking pan. Make sure it's a compact layer.
Step 5: Bake the crust for 20-25 minutes, or until lightly golden brown around the edges.
Step 6: While the crust is baking, prepare the lemon filling. In a separate large bowl, whisk together 2 cups granulated sugar and 1/4 cup all-purpose flour.
Step 7: Gradually whisk in the 1/2 cup fresh lemon juice and 1 tablespoon lemon zest until smooth.
Step 8: Whisk in the 4 large eggs one at a time, until the mixture is well combined and smooth.
Step 9: Once the crust is lightly golden, carefully pour the lemon filling evenly over the hot crust.
Step 10: Return the pan to the oven and bake for another 20-25 minutes, or until the center is just set with a slight jiggle remaining when gently shaken. The edges should be lightly golden.
Step 11: Remove the lemon bars from the oven and let them cool completely in the pan on a wire rack for at least 2-3 hours. For easier cutting and faster setting, you can refrigerate them for at least an hour once cool enough to handle.
Step 12: Once completely chilled, use the parchment paper overhang to lift the entire slab of lemon bars from the pan.
Step 13: Dust generously with powdered sugar just before serving. Use a sharp, warm knife (wiping it clean between cuts) to slice into 16 squares.