In a food processor, pulse flour, sugar, and salt together. Add cubed butter and pulse until the mixture resembles coarse crumbs.

Slowly add ice water, 1 tablespoon at a time, until the dough begins to come together. Divide the dough in half, shape into disks, wrap in plastic, and chill for 30 minutes.

Roll out one disk of dough on a floured surface to about 1/8-inch thickness. Cut into rectangles (about 3x4 inches). Repeat with the second disk.

Mix applesauce and cinnamon in a small bowl.

Place half of the dough rectangles on a parchment-lined baking sheet. Spoon about 1 tablespoon of applesauce mixture onto each.

Brush edges with egg wash, then top with remaining dough rectangles. Press edges with a fork to seal.

Chill the assembled pop-tarts in the fridge for 15 minutes. Meanwhile, preheat the oven to 375°F (190°C).

Bake for 20–25 minutes, or until golden brown. Let cool on a wire rack.

For the glaze, whisk powdered sugar and milk until smooth. Drizzle over cooled pop-tarts and add sprinkles if desired.