Lemon Crumb Bars

3/4 cup unsalted butter melted

1/2 a cup white sugar

1/2 a cup firmly packed brown sugar

3/4 tsp salt

2 tsp vanilla extract

2 cups all purpose flour

1/4 tsp baking powder

Filling

3 large eggs at room temperature, divided

1 cup plus 2 tbsp white sugar

2 Tbsp of cornstarch

2 Tbsp freshly grated lemon zest

1 pinch of salt

3 Tbsp unsalted butter melted and cooled

1/2 freshly squeezed lemon juice

Pre-heat oven to 350 F. Line a 9x9 inch square baking pan to hang on all sides. For the crust and crumbs, stir together melted butter, white sugar, brown sugar, salt, and vanilla until thoroughly combined. Add in flour and baking powder. Mix until mixture comes together in large clumps. Measure out a loosely packed 1 3/4 cup crumbs and press firmly and evenly into the bottom of prepared pan. Reserve remaining crumb mixture for the topping. Break an egg into a large bowl and whisks for a few seconds. Lightly brush a thin layer of egg over the crust. You will use any egg left in the filling. Place crust in freezer for ten to fifteen minutes while preparing filling. For the filling, to the egg you used as egg wash add the remaining 2 eggs, 1 cup plus 2 tbsp of sugar, cornstarch, lemon zest, and pinch of salt. Whisk until completely smooth and combined. Whisk in the tbsp of melted butter until incorporated. Pour in lemon juice and whisk until combined. Remove crust from freezer and pour the filling evenly over the top. Bake bars in the pre-heated oven for 25 minutes. Remove pan from oven and sprinkled reserved crumbs evenly on top breaking up any large crumbs as needed. return pan to the oven. Bake until crumbs just begin to turn golden 20 to 25 minutes more. Allow bars to cool completely about 30 minutes before cutting and serving.