Preheat your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal. This is crucial for clean bars.

In a large bowl, combine the 2 cups all-purpose flour, 1/2 cup granulated sugar, and 1/4 tsp salt for the crust. Add the cold, cubed unsalted butter. Using a pastry blender, your fingertips, or a stand mixer with a paddle attachment, cut the butter into the flour mixture until coarse crumbs form and the mixture resembles wet sand.

Press the crust mixture evenly into the bottom of the prepared baking pan. Use the back of a spoon or your hands to create a compact, flat layer.

Bake the crust for 15-20 minutes, or until the edges are lightly golden. Remove from the oven and keep the oven on while you prepare the filling.

While the crust is baking, in a separate large bowl, whisk together the 1 3/4 cups granulated sugar and 1/4 cup all-purpose flour for the filling until no lumps remain.

Add the large eggs, fresh lemon juice, lemon zest, and 1/4 tsp salt to the sugar and flour mixture. Whisk vigorously until all ingredients are well combined and the mixture is smooth. Ensure the zest is finely grated to avoid large pieces in the final product.

Carefully pour the lemon filling over the hot, pre-baked crust in the pan. The heat from the crust will help start the cooking process for the filling.

Return the pan to the oven and bake for another 20-25 minutes, or until the filling is set and the edges are lightly golden. The center should still have a slight jiggle, but it will firm up as it cools.

Remove the pan from the oven and let the lemon bars cool completely at room temperature for at least 1-2 hours. Then, refrigerate for a minimum of 2 hours, or preferably overnight, to allow them to firm up completely for clean cuts.

Once chilled, use the parchment paper overhang to lift the entire slab of lemon bars out of the pan. Place on a cutting board.

Before serving, dust generously with powdered sugar using a fine-mesh sieve. Cut into 16 squares or desired shapes using a sharp knife, wiping the knife clean between each cut for perfect edges.