01 - Preheat the oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing overhang on sides for easy removal.
02 - Whisk together flour, baking powder, and salt in a medium bowl until well blended. Set aside for later use.
03 - In a large bowl, whisk melted butter and granulated sugar until smooth and fully incorporated. Add eggs one at a time, whisking thoroughly after each addition. Stir in fresh lemon juice, lemon zest, and vanilla extract until uniform.
04 - Gently fold the dry ingredients into the wet mixture, mixing just until combined and no dry streaks remain. Avoid overmixing to prevent tough texture.
05 - Transfer batter to the prepared pan, spreading evenly with a spatula to create a smooth surface layer.
06 - Bake for 22 to 25 minutes until center is just set and edges are lightly golden. The top should spring back lightly when touched.
07 - Allow brownies to cool completely in the pan on a wire rack. This step is essential for proper texture and clean cutting.
08 - In a small bowl, whisk powdered sugar and fresh lemon juice until smooth and pourable. The consistency should coat the back of a spoon.
09 - Spread glaze evenly over cooled brownies. Sprinkle with additional lemon zest as desired for visual appeal and extra citrus flavor.
10 - Using a sharp knife, cut into 16 equal squares. Wipe knife between cuts for clean edges. Serve at room temperature.