In a medium bowl, stir together 1 cup sugar, 3 cups flour, and baking powder. Mix in 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 top.