Homemade Cherry Pop Tarts

Name: Homemade Cherry Pop Tarts
Ingredients: 1 cup all-purpose flour; 1 tablespoon granulated sugar; 1/2 teaspoon kosher salt; 1/2 cup 1 stick unsalted butter, frozen; 1/4 cup ice water; 2 cups fresh cherries (pitted); 1/4 cup granulated sugar; 2 teaspoons lemon juice; pinch kosher salt; 1 tablespoon cornstarch; 1 tablespoon cold water; 1 large egg (beaten); 1 teaspoon water; 1 tablespoon sugar; 2 tablespoons cherry filling; 1 tablespoon water; 1 1/2 - 2 cups powdered sugar; sprinkles (if using)