01 - Preheat the oven to 350°F. Line an 8x8-inch baking pan with parchment paper to prevent sticking.
02 - In a medium bowl, whisk together flour, baking powder, and salt until well blended. Set aside.
03 - In a large bowl, whisk melted butter and sugar until smooth. Add eggs one at a time, whisking thoroughly after each addition. Stir in lemon juice, lemon zest, and vanilla extract.
04 - Gently fold the dry ingredients into the wet mixture, mixing just until combined. Avoid overmixing to maintain tender texture.
05 - Pour the batter into the prepared pan and smooth the top evenly with a spatula.
06 - Bake for 22–25 minutes, or until the center is just set and edges are lightly golden.
07 - Allow brownies to cool completely in the pan on a wire rack before glazing.
08 - In a small bowl, whisk powdered sugar and lemon juice until smooth. Spread evenly over cooled brownies and sprinkle with extra lemon zest if desired.
09 - Cut into 16 equal squares and serve immediately or store in an airtight container.