Step 1

Preheat oven to 375 F. Grease a 9 x 13 inch baking pan. Stir together the flour, 1 cup white sugar, baking powder, and salt. Cut in the butter, until the butter is in pea-sized pieces. (See note below for an easy tip!)

Step 2

Stir in the beaten egg with a fork. Press half of the dough into the bottom of the baking dish. Combine the blackberries, lemon juice, cornstarch, and sugar in a medium-size mixing bowl and stir to combine.

Step 3

Scatter the sugared berries over the crust in the pan. Sprinkle with the other half of the dough mixture.

Step 4

Bake at 375 F for 30-35 minutes, or until lightly browned. Let cool completely.