Preheat your oven to 350°F (175°C). Grease and line an 8x8-inch baking pan with parchment paper.
In a large bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth.
Add the eggs, lemon juice, and lemon zest. Mix until fully incorporated.
In a separate bowl, sift together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
Pour the batter into the prepared pan and spread evenly. Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean.
While the brownies cool, prepare the lemon glaze by whisking together the powdered sugar, lemon juice, and lemon zest.
Once the brownies have cooled, pour the glaze over the top and spread evenly. Allow the glaze to set before slicing into squares.