Pie Crust: In a food processor (or a bowl) combine flour, salt, sugar, and lemon zest. Pulse (or cut) butter into flour mixture. Continue to pulse a few more times until butter is in pea sized chunks. Pulse in ice water 1 tablespoon at a time until dough begins to come together. (Test your dough by pinching some together with your fingers. If it holds together, it is ready.) Remove from food processor (or bowl) onto a piece of plastic wrap. Form into a disc and wrap in plastic. Place in refrigerator to chill for one hour (or up to two days).
Preheat oven to 375 degrees. Line a baking sheet with parchment paper and set aside.
In a bowl, add blueberries, granulated sugar, lemon juice, lemon zest, flour, and vanilla extract. Stir to combine. Set aside.
Roll out dough onto a lightly floured surface into about a 12" circle. Transfer dough onto parchment lined baking sheet.
Carefully pour blueberry filling into center of pie crust, leaving a 2" border around edges. Fold edges up over filling, overlapping slightly.
In a bowl, whisk together egg and water to make an egg wash. Gently brush egg wash over crust. Sprinkle turbinado sugar over crust.
Bake for 40-45 minutes, or until crust is golden brown and filling is bubbling. Remove from oven and allow to cool before serving.
Store any leftovers in a sealed container at room temperature for 2-3 days.
Optionally, top your galette with a scoop of vanilla ice cream or whipped cream before serving.