Preheat your oven to 350°F (175°C). Grease and line a 9x13-inch baking dish with parchment paper, leaving some overhang for easy removal.
In a large mixing bowl, combine the melted butter and granulated sugar. Mix until well combined and slightly cooled.
Add the eggs, lemon zest, lemon juice, and vanilla extract to the mixture. Whisk well until combined.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, stirring gently until just incorporated. Be careful not to overmix.
Pour the batter into the prepared baking dish, spreading it out evenly.
Bake in the preheated oven for 20-25 minutes or until the edges are lightly golden and a toothpick inserted into the center comes out clean.
Remove from the oven and let it cool in the pan for about 15 minutes. Then, lift out the brownies using the parchment paper and allow them to cool completely on a wire rack.
Once cooled, dust the top generously with powdered sugar. Cut into squares and serve.
Notes
Serve the brownies on a decorative platter with extra lemon slices around them for a bright and cheerful display!