Preheat the oven to 400°F (200°C). Roll out half the pastry and line a 9-inch pie pan; trim crust to the rim of the pan. Loosely cover with plastic wrap and refrigerate.

Combine sugar, tapioca, and cinnamon in a bowl. Toss the mixture with blueberries and sprinkle with lemon juice. Let stand for 15 minutes.

Pour the blueberry mixture into the chilled pie shell and dot with butter. Roll out the top crust into a 10-inch circle and cut into half-inch strips. Weave the strips to form a lattice on top of the filling. Flute the edges.

Bake the pie on a baking sheet to catch drips, in the preheated oven for 40-50 minutes, until the filling is bubbly and the crust is light brown.