Preheat the oven to 375°F. You will need two baking sheets.
In a medium-size saucepan, combine the apple, coconut sugar, 1 tablespoon of the water, and the lemon juice.
Cook over medium heat until bubbly. Cover, lower the heat to low, and cook for 6 to 8 minutes, stirring every couple of minutes to make sure the mixture is not sticking.
Take the pie crusts out of their pouch or pans and lay one on each baking sheet. Let them come to room temperature so that you can unfold them more easily without the dough tearing.
In a small bowl, mix the flour, granulated sugar, and salt. Stir into the bubbling apple mixture until the mixture thickens. This will take about a minute.
Remove from the heat and stir in the butter and vanilla.
Add the frozen blueberries and fold into the hot mixture. Let cool for about 10 minutes. The mixture will become a blueberry color.
Unfold one of the piecrusts on the baking sheet. Set the other aside on the second baking sheet.
Spoon half of the cooled fruit filling onto the center of the open crust.
Carefully fold over the piecrust to meet the other edge so that you have a half-moon shape.
Press the edge together, roll the edge by over one turn all around the open edge, and then press the rolled edge with fork tines for an even better seal.
Cut a few small slits on the top of the piecrust. Repeat this process with the other pie crust and remaining filling, on the other baking sheet.
Bake for 25 to 35 minutes, until the crust is golden brown. Switch the positions of the baking sheets about 15 minutes into baking.
Remove from the oven when golden brown and let cool on the baking sheets.
Use a metal spatula to loosen the pies from the baking sheets and cut each half-moon pie into fourths.