Prepare pie dough. (If you haven't already, separate the dough into two balls. One ball will become the bottom crust of the pie, and the other ball will become the top crust.) Turn out one ball of dough onto a floured surface, and roll into a thin circle. Circle must be large enough to fit your 9" pie plate with (at least) a 1/2" overhang. Fit the circle of dough into the pie plate and set aside. Roll out the second ball of dough into a thin circle. 

Preheat oven to 375 degrees F. 

In a large bowl, combine sugar, corn starch, and cinnamon. Mix with a fork until well combined. 

Add clean blueberries to the sugar mixture, and toss to combine. Add zest and fresh lemon juice, and toss to combine. 

Pour blueberry mixture into the prepared pie dish (fitted with the bottom crust). Smooth out the berries so it has a flat surface. 

Prepare the top crust of the pie. If you choose to do a lattice-top pie, follow the below instructions.*  Otherwise, move the top crust to fit over the top of the pie. Seal the "overhang" of the bottom crust to the "overhang" of the top crust. (Seal with a fork, or pinch it closed with your fingers. 

In a small bowl, mix together the egg and water for the egg wash. Using a pastry brush, brush the egg wash evenly onto the top pie crust. Sprinkle the top pie crust with coarse sugar. Slice a few slashes into the top of the pie for steam to escape. 

Bake the pie for approximately 45 minutes, or until pie filling is bubbly and crust is golden brown. Serve warm!

* Making a lattice-top pie crust is easy, once you get the hang of it. After rolling the top crust into a circle, slice it into 1" strips using a pizza cutter or pastry wheel. Add the first strip of dough to the top of the pie, directly across the middle. Drape the second strip across the first strip so the two strips make an "X." Now, begin to weave in an under-over pattern. So, take the third strip of dough and lay it on the pie so the middle of the strip touches the center of the second strip. All three strips will look like an "H." Now, the first strip will under the others. So, gently fold back the edge of the first strip, and lay down a new one across the pie, and fold the first strip back down OVER the new strip. Now, you begin to see how the strips of dough goes under one, then over the next. Getting the hang of it? Continue to lay down the strips of dough in this manner until the lattice top is complete! If a strip of dough tears during the process, just pinch it back together to mend the tear. And, if you make a mistake, just correct and move on. It's pie! When the lattice top is finished (first, admire your handiwork), you'll see some dough overhang. Trim the overhang so there's 1/2-1" dough remaining. Roll this dough under and pinch it closed with your fingers to seal. Brush with egg wash (1 egg and 1Tbs water mixed together), and sprinkle with coarse sugar. Bake the pie at 400 degrees F until crust is golden brown and pie filling is bubbly.