1. In a large bowl, whisk together gluten-free flour, sugar, and salt.

2. Cut in cold butter with a pastry cutter or fork until mixture resembles coarse crumbs.

3. Beat the egg and mix in. Gradually add ice water, 1 tbsp at a time, until dough holds together but isn’t sticky.

4. Divide dough in half, shape into disks, wrap in plastic, and chill for 30 minutes.

5. Preheat oven to 375°F (190°C) and line a baking sheet with parchment paper.

6. Mix cornstarch and water in a small bowl, then stir into jam.

7. Roll out one disk of dough between two sheets of parchment to about 1/8 inch thick. Cut into rectangles (about 3×4 inches).

8. Place half the rectangles on the baking sheet. Spoon 1–2 tsp of jam mixture into the center of each.

9. Top with remaining dough rectangles, pressing edges to seal. Use a fork to crimp edges and poke holes in tops.

10. Bake for 20–24 minutes or until golden. Cool completely before glazing.

11. For glaze, whisk powdered sugar, milk, and vanilla. Drizzle over cooled tarts and top with sprinkles.