In a food processor, combine gluten-free flour blend, sugar and salt. Then add in the cold, cubed vegan butter.
Pulse 6-8 times, until you have a mixture that resembles coarse meal and the butter is the size of peas.
Add one tablespoon of water at a time, pulsing in between, until you able able to pinch the dough between your fingers and it holds together.
Turn the dough mixture out onto a clean surface and knead together into a ball. Wrap in plastic wrap and refrigerate for at least one hour.
In a small bowl, stir together sugar, cornstarch, cinnamon, and lemon zest.
Pour the blueberries into a separate bowl.
Coat the blueberries with the lemon juice.
Stir in the sugar mixture until the blueberries are completely coated.
After the pie dough is chilled, roll it out to a 1/8 inch thickness.
Cut out circles with a 5-6 inch diameter.
Add 1-2 tbsp of blueberry filling to the center of the dough.
In a small bowl, whisk together the egg yolk with 2 tbsp of water.
Brush egg wash on the edge of the dough circles to create a seal.
Fold dough circle in half and crimp the edges with a fork.
Chill filled circles for half and hour before baking.
In the meantime, preheat the oven to 375 degrees Fahrenheit.
Remove pies from the refrigerator and brush tops with egg wash.
Cut a small slit in the top of each pie and bake for 20 minutes or until the top is golden brown. Let cool completely before serving.