Preheat oven to 400 degrees. Stir together cream cheese, 1/2 cup granulated sugar, lemon zest, and egg until smooth. Toss blueberries with 1/4 cup granulated sugar, lemon juice, and flour.
Lay 1 dough round on a parchment-lined baking sheet and cut into quarters. Spoon 1 heaping tablespoon cream cheese mixture into center of each quarter. Spoon 2 tablespoons blueberry mixture on top. Brush edges with cream and bring opposite corners together to form triangles; trim if needed. Crimp edges to seal, brush tops with cream, and sprinkle with sanding sugar. Repeat with remaining dough round and fillings. Cut a small vent in each pie and bake until golden, 20 to 25 minutes, rotating sheets halfway through. Let cool completely on wire racks before serving.