• Preheat oven to 350°F and prepare a 9x9-inch pan by lining it with parchment paper (or lightly grease and flour). (You could use a 9x13-inch pan for more servings, but the bars will be thinner.)
• In a large bowl, combine the melted butter and brown sugar. Stir well.
• Add the eggs one at a time, stirring well after each addition.
• Stir in the lemon juice and lemon zest.
• In a separate, medium-sized bowl, whisk together the flour, cornstarch, baking powder, and salt.
• Gradually stir the flour mixture into the butter and egg mixture until completely combined.
• Spread the batter evenly into the prepared pan. Bake 35-45 minutes, or until the edges are turning golden brown. (If you are using a 9x13-inch pan, bake for 25-30 minutes.)
• Allow brownies to cool before glazing.

Glaze

• In a medium bowl, combine the confectioners' sugar and lemon juice. Whisk until smooth.
• Pour the glaze over the cooled brownies and serve.