To make the crust: Combine the flour, buttermilk powder, and salt. Work in the fat in two batches, leaving some pieces as large as your thumbnail., Sprinkle in ice water 1 tablespoon at a time, tossing with a fork and adding water until the dough is completely cohesive., Divide the dough in two pieces; one should be about twice as big as the other. Wrap in plastic, and chill for 30 minutes before rolling., Roll the crust about 1/8" thick, and about 12" to 13" wide, large enough to fit a 9" deep-dish pie pan (at least 1 1/2" deep). Place the crust in the pan, and refrigerate the pie while you preheat the oven to 425°F., To make the filling: In a large bowl, whisk together the sugar, thickener, and cinnamon., Add the berries, lemon juice, and melted butter. Scoop the mixture into the prepared crust., Roll out the top crust, making a lattice if you like; place it over the berries. Trim any excess overhang, and crimp the edges together. Cut several slashes to allow steam to escape (if you haven't made a lattice crust). Spritz with water, and sprinkle with sparkling sugar or cinnamon-sugar., Bake the pie for 15 minutes, then reduce the oven heat to 350°F and bake for another 40 to 50 minutes, covering the edges if they seem to be browning too quickly. When done, the filling will be bubbling, and the crust golden brown., Remove the pie from the oven, and cool it for at least 1 hour before serving.