Preheat oven to 375 degrees F. Line an 8" square pan with foil or parchment and lightly coat with cooking spray.

To make the crust and crumb topping, combine the flour blend (measure the flour blend by lightly spooning into the measuring cup and leveling off with the back of a knife), confectioner's sugar, lemon zest and salt in a large bowl. Cut in the butter or coconut oil with a fork or pastry blender until crumbly. Set aside 3/4 cup of the crumb mixture for the topping. Press the remaining mixture in the bottom of the prepared pan. Bake the crust for 10 minutes.

To make the filling, stir together the sugar and cornstarch in a large bowl. Add the berries and lemon juice and toss gently to combine. Spread berry mixture evenly over the baked crust. Sprinkle the remaining 3/4 cup crumb mixture over top of the berries.

Bake for 45 to 50 minutes, or until bubbly and golden brown (note that if using coconut oil, the bars will not brown like they do when made with butter). Cool completely on a wire rack. Lift bars out of pan with the foil or parchment and cut into bars.