1. Preheat oven to 375F. Grease a 9x13 pan and set aside.

Make the Crust/Crumble:

1. In a medium bowl, combine 1 c. sugar, flour, baking powder and salt. Using a pastry cutter, cut butter, lemon zest and egg into the dry ingredients. Dough will be crumbly.

Make the Blueberry Filling:

1. In another bowl, stir together lemon juice, remaining 1/2 c. sugar and cornstarch. Gently fold in blueberries.

Assemble & Bake:

1. Pour half of flour mixture into prepared baking pan. Gently pat into an even layer. Top with blueberry mixture and sprinkle evenly with remaining flour mixture.

2. Bake for 40-60 minutes, until top is slightly browned.

3. Remove from oven and allow to cool completely before cutting.

4. Store, covered with plastic wrap, at room temperature or in the fridge. At room temperature, the bars kept fresh for at least 3 days (at which point I had eaten or gifted the entire pan).