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, and baking powder. Mix in salt and cinnamon, if desired. Use a fork or pastry cutter to blend in the shortening and egg. Dough will be crumbly. Pat half of dough into the prepared pan.
In another bowl, stir together the sugar and cornstarch. 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. Cool completely before cutting into squares.