If fresh blueberries aren’t available, drain two 15-ounce cans of whole blueberries packed in water or light syrup. Rinse and dry the berries well before using in the filling. Avoid pie filling products—they contain added sugar and thickeners that will throw off your ratios.

Prepare or buy a 9-inch pie shell
If you’re making it from scratch, my favorite pie crust recipe is at How to Make Pie Crust: The Complete Guide.

Make the Blueberry Filling

1. 1. Combine the filling:  In a large bowl, gently mix 5 cups of blueberries (thawed and drained if frozen or canned), ¾ cup of sugar, ¼ cup of cornstarch, 1 tablespoon lemon juice, ¼ teaspoon cinnamon, and a pinch of salt.
   2. Toss the berries: Coat the berries evenly but gently to avoid crushing them.
   3. Taste test: If the berries are extra sweet, use 1–2 tablespoons less sugar; if tart, add more sugar or a bit more lemon juice.

Assemble and Bake the Pie

1. 1. Add the blueberry filling into the pie shell and gently smooth the top.
   2. Scatter 2 tablespoons of butter in small pieces across the berries.
   3. Cover with another piece of rolled dough (full crust or lattice), press edges to seal, and trim excess. Crimp the edges for a neat finish. Cut four short vents in the top if using a full crust.
   4. Use a pastry brush to paint the crust with milk or a beaten egg for shine, then chill the pie in the fridge for 15–20 minutes.
   5. Place the pie on a lower oven rack. Bake at 425°F (220°C) for 15 minutes, then reduce heat to 350°F (175°C) and continue for 35–40 minutes. The crust should be golden brown. Filling should bubble through the vents.
   6. If the crust’s edges darken too much, shield them with foil.
   7. Let the pie cool for at least 3 hours before slicing to give the filling time to set.