blueberry crumb bars

Preheat the oven to 375 degrees F (190 degrees C). Grease a 9×13 inch pan.In a medium bowl, stir together 1 cup sugar, 3 cups flour, baking powder, salt, and lemon zest. Use a fork or pastry cutter to blend in the butter and egg. Dough will be crumbly. Pat half of dough into the prepared pan.In another bowl, stir together the sugar, cornstarch and lemon juice. Gently mix in the blueberries. Sprinkle the blueberry mixture evenly over the crust. Crumble remaining dough over the berry layer.Bake in preheated oven for 45 minutes, or until top is slightly brown. (This took an extra 10 to 15 minutes in my oven.) Cool completely before cutting into squares.