Prepare the Pan: Preheat the oven to 325°F (165°C). Lightly grease a 9×9-inch metal baking pan, then line it with parchment paper and set aside.
Melt the Chocolate: Place the chopped white chocolate and cubed unsalted butter in a double boiler over medium-low heat. Stir continuously so the white chocolate heats evenly. Once the mixture is melted and smooth, remove it from the heat.
Whisk the Wet Ingredients: Add the eggs, egg yolks, granulated sugar, lemon zest, and vanilla extract to a large bowl. Whisk until the mixture becomes pale and smooth. An electric hand mixer can also be used on high speed.
Combine the Chocolate Mixture: Pour the melted white chocolate and butter into the egg mixture. Whisk until everything is thoroughly combined and smooth.
Add the Dry Ingredients: Add the flour and salt to the wet mixture. Using a rubber spatula, gently fold until just combined, taking care not to overmix.
Fill the Pan: Transfer the lemon brownie batter to the prepared pan. Use a mini offset spatula to spread and smooth the batter into an even layer.
Bake the Brownies: Bake at 325°F (165°C) for 32–36 minutes. If the brownies begin becoming too brown toward the end of baking, loosely cover the pan with parchment paper.
Cool Completely: Place the baked brownies in the pan on a wire rack and allow them to cool completely before removing or glazing.
Release the Brownies: Once completely cool, run a butter knife around the edges to loosen the brownies from the pan. Gently lift the parchment paper to release the brownies.
Prepare the Lemon Glaze: In a medium bowl, mix the powdered sugar, fresh lemon juice, pinch of salt, and 1 teaspoon lemon zest until combined into a glaze.
Glaze the Brownies: Pour the lemon glaze over the cooled brownies. Use a mini offset spatula to spread it into an even layer.
Finish the Topping: Allow the glaze to set, then sprinkle additional lemon zest over the surface.
Cut and Serve: Cut the glazed brownies into 16 squares and serve.
