Step 1

Preheat oven to 375 degrees F. Lightly grease a 9x13-inch baking pan.

Step 2

Make the Crumb: In a medium bowl, whisk together the flour, sugar, baking powder and salt. Use a fork or pastry cutter to blend in the butter, and then the egg (the dough will be crumbly). Press half of dough into the prepared pan.

Step 3

Make the Filling: In a separate large bowl, whisk together the sugar, cornstarch and lemon juice. Gently fold in the blueberries to coat evenly with the sugar mixture. Spread the blueberry mixture evenly over the crust, drizzling any excess juice in the bowl over the filling. Crumble the remaining dough evenly over the blueberry layer.

Step 4

Bake for 45 to 50 minutes, or until the top is light golden brown. Cool completely before cutting into squares. Leftovers can be stored in an airtight container or wrapped in plastic wrap at room temperature or in the refrigerator for up to 4 days.