Prepare the Crust

Cup of Yum
1. If using a food processor: Combine the flour, sugar, salt, and baking powder in the bowl of a food processor fitted with the metal blade. Pulse a few times to combine. Add the butter and pulse until the mixture is crumbly with lots of pea-size clumps of butter within. Add the water and pulse until the mixture is evenly moistened and very crumbly. Dump the dough crumbles onto a clean work surface and divide into two even piles. Make two balls of dough and pat each one into a 5-inch disc. Wrap the discs in plastic and refrigerate for at least 45 minutes and up to 3 days.
2. If making by hand: In a large mixing bowl, whisk together the flour, sugar, salt, and baking powder. Add the butter and use a pastry cutter or two knives to cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Gradually add the ice water, mixing with a fork, and then your hands, until the dough comes together into a ball. Divide into two balls of dough and pat each one into a 5-inch disc. Wrap the discs in plastic and refrigerate for at least 45 minutes and up to 3 days.

Prepare the Filling

1. In a large bowl, combine the blueberries, lemon zest, lemon juice, sugar, salt, and tapioca flour. Toss until combined; don’t worry if the mixture is powdery.

Preheat the Oven

1. Preheat the oven to 425°F (220℃) and set an oven rack in the lower third position. Line a baking sheet with aluminum foil (the foil will catch the juices that bubble over from the pie, making for easy clean up).

Prepare the Bottom Crust

1. Remove one disc of dough from the refrigerator. Lightly dust a clean work surface with flour and place the dough on it; sprinkle a bit of flour over the dough as well. Gently knead the dough with your hands just until it becomes soft and malleable (avoid overworking it—you want it just supple enough to roll out). Roll the dough out into a 13-inch (33-cm) circle, adding more flour as needed to prevent sticking. Carefully lift the dough by draping it over your rolling pin and transfer it to a 9-inch (23-cm) deep-dish pie pan (it should be 2 inches/5 cm deep). Gently press the dough into the pan, making sure to ease it into place without stretching. Trim the edges of the dough to extend about ½ inch (1.25 cm) beyond the pie pan's lip.

Fill the Pie

1. Transfer the filling into the crust and press into an even layer (do not mound). Dot the berries with the butter cubes. Refrigerate while you prepare the top crust.

Prepare the Lattice Top Crust

1. Remove the top disc of dough from the refrigerator and roll it out into a 10x15-inch (25x38-cm) rectangle, following the same process described earlier. Using a pizza or pastry cutter, trim the edges and then cut the dough into 14 one-inch (2.5 cm)-wide strips. Retrieve the filled pie from the refrigerator. Lay half of the strips horizontally over the pie filling, leaving about 1/2 inch (1.25 cm) of space between each strip. Fold back every other strip halfway over itself. Place one strip of dough vertically over the unfolded strips. Unfold the folded strips over the new strip, then fold back the alternating strips that were previously left unfolded. Lay another strip of dough parallel to the first vertical strip, about 1/2 inch (1.25 cm) away from it. Repeat the process, folding back the strips as necessary, until the lattice crust covers the entire pie. Trim any excess dough from the edges of the lattice strips, leaving a slight overhang. Fold the edges of the bottom crust over the lattice strips, then crimp or flute the edges to seal the pie.

Bake

1. Place the pie on the lined baking sheet and bake at 425°F (220℃) for 20 minutes. Reduce the oven temperature to 375°F (190℃) and continue baking for an additional 60 to 70 minutes, or until the crust is golden brown and the filling is bubbling both on the edges and in the center. If you have a digital thermometer, it should be at least 213°F (100℃) in the center. Keep an eye on the pie during the second half of baking and tent lightly with foil if it’s getting too brown on top (I usually tent it at the 40-minute mark in the second phase).
2. Immediately move the hot pie off the foil and place on a heat-proof surface. If necessary, take a wad of wet paper towels and wipe any blueberry juice from the edges (it gets extremely sticky as it dries). Let the pie cool completely before slicing, at least 8 hours or overnight. If you have a digital thermometer, it should be 78°F (26℃) or lower in the center before slicing. Resist the temptation to cut into the pie while it’s even slightly warm, or you will end up with blueberry soup!
3. Once cooled, you can keep the pie at room temperature for up to 2 days, covering it loosely with foil to prevent it from drying out. If you need to store the pie for longer than 2 days, place it in the refrigerator, covered with plastic wrap or aluminum foil, and store for up to 4 days.