Combine flour, orange zest,(I use fresh from the orange used for the juice and lots of it) sugar and salt in a mixing bowl; stir to blend. Using a pastry blender or 2 knives, cut butter into flour mixture until all resembles coarse meal. Combine orange juice with water or use 3 Tbsps orange juice. Add liquid by Tbsp, mixing gently with a fork, just until dough begins to hold together in clumps. If necessary, an extra spoonful of water may be added. Gather dough up and shape into a flat, round disk.
Chill at least 1 hour.
On lightly floured surface, roll dough to about 1/8" thickness, in big enough circle to overhang 9" pie plate by almost 2". Ease pastry into pie plate being careful not to stretch it. Fold excess under, crimp decoratively. Prick bottom and sides.
Freeze about 20 minutes while oven pre-heats to 375°F.
Bake shell for 15 minutes or until golden brown. Cool on wire rack while you make the filling.
For the filling:.
Stir together the sugar and cornstarch in heavy-bottomed 3 quart saucepan. Stir in orange juice and 2 cups of the blueberries. Cook, stirring constantly, over medium-high heat until mixture is thickened and just comes to the boil (7 to 10 minutes). Remove from the heat and gently fold in remaining berries. Mound filling into cooled crust and chill for at least 1 hour before serving.
For real decadence top with whipped cream.