Preheat the oven. Set your oven to 425°F (220°C). Place a baking sheet on the middle rack to heat up. This helps the bottom crust bake evenly.

Make the filling. In a large bowl, combine blueberries, sugar, cornstarch, lemon zest, lemon juice, salt, and cinnamon if using. Toss gently to coat. Let it sit for 10 minutes so the berries release some juices.

Prepare the crust. Roll out one crust and fit it into a 9-inch pie plate. Leave a little overhang. Keep the second crust chilled.

Fill the pie. Spoon the blueberry mixture into the crust, scraping in all the juices and cornstarch. Dot the top with the butter pieces.

Add the top crust. Roll out the second crust and place it over the filling. Trim excess, then fold and crimp the edges to seal. Cut 4–6 slits on top for steam, or make a simple lattice if you like.

Brush and sugar. Brush the top with egg wash. Sprinkle with coarse sugar if you want that bakery sparkle and crunch.

Bake hot, then lower the temp. Place the pie on the preheated baking sheet. Bake at 425°F (220°C) for 20 minutes. Reduce heat to 375°F (190°C) and bake 30–40 minutes more, until the crust is deep golden and the filling is bubbling steadily through the vents.

Shield if needed. If the edges brown too fast, cover the rim with foil or a pie shield during the last 20 minutes.

Cool completely. Set the pie on a rack and cool at least 3–4 hours. This allows the filling to set so your slices are clean and not soupy.

Serve. Enjoy at room temperature or slightly warm. It’s great plain, with whipped cream, or with a scoop of vanilla ice cream.