01 - Preheat the oven to 350°F. Line an 8x8-inch baking pan with parchment paper, ensuring the paper extends slightly over the edges for easy removal.
02 - In a medium bowl, whisk together the flour, baking powder, and salt until thoroughly blended. Set aside.
03 - In a large bowl, whisk the melted butter and granulated sugar until smooth and well combined. Add the eggs one at a time, whisking thoroughly after each addition. Stir in the lemon juice, lemon zest, and vanilla extract.
04 - Gently fold the dry ingredients into the wet mixture, mixing just until combined. Be careful not to overmix, as this can result in tough brownies.
05 - Pour the batter into the prepared pan, using a spatula to spread it evenly and smooth the top surface.
06 - Bake for 22-25 minutes, or until the center is just set and the edges are lightly golden. A toothpick inserted into the center should come out with moist crumbs.
07 - Allow the brownies to cool completely in the pan on a wire rack before applying the glaze.
08 - In a small bowl, whisk the powdered sugar and lemon juice until smooth and drizzle-consistency. Spread the glaze evenly over the cooled brownies and sprinkle with additional lemon zest if desired.
09 - Cut into 16 equal squares and serve. For clean cuts, wipe the knife blade between slices.