• Preheat oven to 375° and right before adding crumb mixture, spray a 9 x 13 baking dish with a non stick spray. 

For The Blueberry Lemon Filling

• In a medium mixing bowl, whisk sugar and corn starch together.
• Add blueberries, zest from lemon and fresh lemon juice. Stir and let sit while making the crumb bars dough, stirring occasionally.

For The Crumb Bars and Topping

• In a large mixing bowl, whisk flour, sugar, brown sugar, baking powder, salt and cinnamon together until combined. 
• Using a pastry blender or a fork, cut butter into flour mixture until crumbly. 
• In a small bowl, whisk egg and vanilla together and add to flour mixture once butter has been added and mixture is crumbly. Continue using pastry blender until combined. 
• Remove half of crumb mixture (approximately 3 cups) and press into prepared baking dish. 
• Stir blueberries and then add to the top of the crumb mixture.
• With the remaining crumb mixture, squeeze with hands to combine as the crumb mixture is added over blueberries. 
• Place in the oven uncovered and bake for approximately 45 minutes or until crumb topping is slightly browned.
• Let cool completely before cutting into squares.