Preheat oven to 400°F (200°C)
In food processor, combine gluten-free flour blend, xanthan gum, cornstarch, and salt
Cut in cold butter until mixture resembles coarse sand
Add 3-4 tablespoons ice water, mixing until dough forms a ball
Wrap dough in plastic, chill 30 minutes
On floured surface, roll dough into ¼ inch thickness
Cut into 4.5 inch squares, cut each corner diagonally to create 12-inch diagonals
Fill half with brown sugar-cinnamon mixture
Fold unfilled half onto filling, press edges to seal
Cut cooled pastries into individual pop tarts
Bake until golden, 8-10 minutes
Mix confectioners’ sugar, water, and cinnamon for glaze
Dip tops in glaze and let set