These blueberry bars have delicate flaky layers of a shortbread-like dough that sandwich together a generous filling made from fresh blueberries. Fresh lemon juice and zest add brightness!
Place an oven rack on the center shelf and preheat the oven to 375 degrees F. Grease a nonstick 8x8 inch pan with butter or baking spray.
In a medium-sized bowl, whisk together the flour and lemon zest, breaking up any clumps. Whisk in the sugar, baking powder, and salt until evenly combined. Use a fork or pastry blender to cut in the butter and egg. The dough will be crumbly. Press half the dough into the prepared pan.
In a separate medium-sized bowl, stir together the sugar, cornstarch, lemon juice and vanilla until smooth. Add the blueberries and gently toss with a spatula to combine. Pour the blueberry mixture evenly over the crust. Crumble the remaining dough over the blueberry layer.
Bake for 38-42 minutes, until the top is golden brown and the sides are slightly bubbly. Cool to room temperature before cutting into squares. Depending on the desired portions, these can be cut to 9 larger squares, 16 smaller squares, or 12 medium rectangles.
Store leftovers in an airtight container in the refrigerator for up to 5 days.