• Preheat the oven to 350°F. Grease and line an 8x8 baking pan with parchment paper. Set aside.
• Place the butter and white chocolate in a microwave safe bowl. Microwave for 1 minute, then stir to fold in the melted butter with the chocolate. Continue to cook in 20-30 second increments, stirring in between until everything is completely melted. Set aside to cool.
• Combine the sugar and lemon zest in a large mixing bowl, rubbing the sugar and zest between your fingertips to release the oils in the lemon. Add the eggs, egg yolk, and vanilla, stirring with a whisk until completely combined. Then fold in the slightly cooled white chocolate mixture.
• Add the flour, salt, and baking powder to the wet ingredients, folding gently with a rubber spatula. Last, stir in the fresh lemon juice, mixing only until incorporated. Pour into the prepared pan.
• Bake for ~22-25 minutes. The edges will look golden brown, (the tops won't be browned), and a toothpick inserted in the center should come out mostly clean, a few moist crumbs are what you want. Allow to cool completely.

Lemon Glaze

• Whisk the powdered sugar and lemon juice in a small bowl (it should be thick, but pourable). Spread over the cooled brownies, finishing with extra lemon zest, and allow to set for 20-30 minutes. You can speed this up by putting them in the fridge. Slice and serve - these will keep for several days in the fridge, or can also be frozen for several weeks.