To make filling and bake pie: Stir together 1/2 cup sugar and tapioca in a mixing bowl. Stir in 1 teaspoon lemon zest and 1 tablespoon juice. Add blueberries and stir gently to mix. Spoon the filling into the prepared crust. Cover loosely with foil and set in the middle of the oven, with a baking sheet placed on the rack below to catch any drips. Bake for 55 to 65 minutes, or until the berries are juicy and bubbling. (Frozen berries will take about 10 minutes longer.) Uncover the pie, sprinkle evenly with the reserved streusel topping and bake for 12 to 15 minutes longer, or until the streusel is golden. Cool on a wire rack for 30 minutes, then cool completely in the refrigerator, about 2 hours.