Makes 9+ bars (depending on how you cut them)
For the crust and crumb topping
1/2 cup white sugar
1/2 teaspoon baking powder
1 1/2 cups flour
Pinch of salt
Zest of 1/2 of a lemon
1/2 of a lightly beaten egg
1 stick cold, unsalted butter, cut into pieces
For the blueberry filing
2 cups fresh blueberries
Juice of 1/2 of a lemon
1/4 cup white sugar
2 teaspoons cornstarch
Preheat the oven to 375 degrees. Grease an 8 or 9 inch baking dish and set aside.
To make the crust:
In a large bowl, mix the sugar, baking powder, flour, salt, and lemon zest. Add the egg and then the butter pieces and use a dough blender or knives to cut the butter into the flour mixture. Press half of the dough into the greased pan.
In a large bowl, mix the blueberries, lemon juice, sugar, and cornstarch until well combined. Spread the mixture evenly over the crust. Crumble the remaining dough over the blueberries.
Bake for 45 minutes until the crust is lightly browned. Cool completely before cutting into bars.