Preheat the oven to 350°F. Prepare an 8×8" pan by spraying with cooking spray or lining with parchment paper, and set aside.

In a large bowl or the bowl of a stand mixer, beat together the softened butter, granulated sugar, and zest of one lemon until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Then add 1 Tablespoon of lemon juice.

Add the all-purpose flour and baking powder, and mix until just combined.

Pour the batter into the prepared pan and smooth into an even layer.

Bake for 20-25 minutes, or until a toothpick inserted into the brownies comes out clean. Let cool for 10-15 minutes.

For the glaze, whisk together powdered sugar, 1½ Tablespoons of lemon juice, and the zest of ½ lemon, then pour over the brownies, spreading evenly to coat.

Let cool completely before slicing into squares.