Preheat your oven to 350° F. Line a 9" x 13" pan with parchment paper, leaving an overhang. Set aside.
In a large bowl, whisk together 2 cups of all-purpose flour, 1.5 cups of sugar, ½ teaspoon of baking powder, and ¼ teaspoon of kosher salt. Add the zest from 2 large lemons and whisk again.
In a small bowl, whisk together 1 cup of melted unsalted butter, 4 large eggs, ⅓ cup of freshly squeezed lemon juice, and 1 teaspoon of pure vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until combined. Spread evenly in the prepared pan.
Bake for 20 minutes or until a toothpick comes out clean. Let cool completely on a wire rack.
For the glaze, whisk together 1.5 cups of powdered sugar, 2 tablespoons of freshly squeezed lemon juice, and the zest from 1 large lemon until smooth.
Drizzle the glaze over the cooled bars and spread evenly. Refrigerate for 2 hours.
Run a knife around the perimeter and lift the bars out using the parchment overhang. Cut into squares and enjoy!
