Spray a 10x10 Pan with cooking spray and preheat your oven to 350 degrees.
With an electric mixer mix Butter, Lemonade, and Granulated Sugar until its a light and fluffy like consistency. Afterwards add in your Vanilla, Eggs (and egg yolks) and incorporate. Make sure mixer's on low and add in flour and baking powder and mix well.
Spread batter evenly into your pan and bake for 15-20 minuteedges begin to golden and center is JUST sets. You don't want to over bake it.
To make your glaze you want to combine the Powdered Sugar, Lemonade or Lemon Juice (whichever you prefer) and Zest. After it's mixed pour it over your brownies and allow to set for approximately 45 minutes -1 hour.