Martha bakes small pies so that every guest gets one for dessert.
Heat oven to 425 degrees. Line a baking pan with parchment paper; set aside. Combine blueberries, sugar, flour, and lemon zest in a large bowl. Gently toss to coat blueberries. Set aside.
On a clean, lightly floured work surface, roll out half the dough into a 1/8-inch-thick square. Using a sharp knife, cut the square into quarters, and carefully drape each quarter over a 5-inch pie tin.
Place 1 1/2 cups blueberry mixture in each pie tin, mounding berries in the center. Dot each pie with 1 1/2 teaspoons butter.
Again, on a clean, lightly floured work surface, roll out remaining dough into a 1/8-inch-thick square. Using a sharp knife, cut square into quarters. With a 1-inch round biscuit cutter, cut a hole from the center of each quarter. Carefully drape each quarter over blueberries so steam hole is centered. Press edges together to seal. Trim edges around pie plates to form a 1-inch lip.
Dampen the 1-inch lip of dough with water. Using scissors, snip inward from outside edge of pie at 3/4-inch intervals, making each cut about 3/4 inch deep. As you cut the dough, carefully fold alternating tabs to create the bear-tooth crimping design. Return to refrigerator until chilled, about 30 minutes.
Place pies on prepared baking pan. Brush each pie with water, and sprinkle with sugar. Transfer to oven, and bake until crust is golden brown, about 20 minutes. Reduce heat to 375 degrees. and continue baking until blueberry juice begins to bubble up, 15 to 20 minutes more. Transfer pies to a wire rack to cool.