Start by freezing your unsalted butter and shortening until very cold, about 30 minutes. In a large mixing bowl, whisk together the gluten-free all-purpose flour blend, granulated sugar, and salt. Cut the chilled fats into the flour mixture until it resembles coarse crumbs.

Mix in the large eggs, apple cider vinegar, and ice-cold water. Stir until the dough comes together; it should be sticky. Shape into a ball, wrap in plastic wrap, and chill in the refrigerator for 45 minutes.

Preheat your oven to 350°F (175°C). Roll out half of the dough on a lightly floured surface to about 1/4 inch thick. Cut into 3x4-inch rectangles. Repeat with the remaining dough for the tops.

Take half the rectangles and spread 2 teaspoons of gluten-free seedless strawberry jam in the center. Place the remaining rectangles on top, sealing the edges by crimping with a fork and poking holes in the tops for steam.

Brush the tops with an egg wash, place on a baking sheet lined with parchment paper, and bake for 20-25 minutes until golden brown. Cool on the baking sheet for 5 minutes before transferring.

Whisk together the powdered sugar, pure vanilla extract, and water until smooth. Once cooled, pour or spread the glaze over the pop tarts and let it set before serving.