Preheat oven to 375° F. Line a 9x13-inch baking dish with parchment paper and set aside.
In a medium bowl, combine the flour, 1 cup of sugar, baking powder, salt, and lemon zest. With a pastry cutter, cut in the butter and the egg. The dough will be very crumbly. Pat half of the crumb mixture into the prepared dish.
In another bowl, combine ½ cup sugar, lemon juice, and cornstarch. Gently fold in the berries and pour evenly over the crust. Take the other half of the crumb mixture and sprinkle on top of the berries.
Bake for 45-50 minutes until the top has slightly browned.
Let bars cool completely to room temperature (or chill in the fridge for even sturdier slices), then use the parchment paper to lift the bars out of the pan and transfer to a cutting board.
Store crumb bars at room temperature for up to 2 days, or in the fridge for up to 7 days (my preferred storage method).
Video
Notes
NOTES:
Can use fresh or frozen berries. If using frozen, do not thaw before using and increase cornstarch to 1 tablespoon + 1 teaspoon.
This recipe can be used with various fruits, either individually to combined. If using fruit like peaches, strawberries or apples, chop into 1-inch pieces.