Using a hand mixer, mix together the butter and sugar in a medium-sized bowl until well blended. Add the flour, cornstarch, and salt and mix until combined.
Press the dough firmly into a lightly buttered 5x5-inch baking dish using your fingertips or the back of a spoon.
Bake 18-20 minutes, until lightly golden. Remove from the oven and set aside to cool, about 20 minutes.
Make the filling
In a small bowl, toss the blueberries with sugar, flour, lemon zest, and lemon juice. After the ingredients are well combined, pour them over the cooled cookie crust.
Place the baking dish on a baking sheet and bake for 45 to 50 minutes.
Remove the pie from the oven to cool, 2 to 3 hours.
Video
Notes
Thaw and Drain: If using frozen berries, let them thaw and drain excess liquid to avoid a soggy pie.
Sweetness: Adjust the sugar based on the sweetness of your berries and your preference.