In a saucepan, off the heat, combine sugar and cornstarch. Add the applesauce. Bring to a boil over medium heat, stirring constantly with a wooden spoon. Add the apple. Allow to cool. Cover and refrigerate for about 1 hour or until the filling is at room temperature.
Line a 43 x 30-cm (17 X 12-inch) baking sheet with parchment paper.
On a floured work surface, roll out the dough into two 35 x 15-cm (14 x 6-inch) rectangles. Place on the baking sheet. Cover and refrigerate for 30 minutes.
With the rack in the middle position, preheat the oven to 200 °C (400 °F).
On a work surface, cut a rectangle of dough into 12 strips of about 1 x 35-cm (1/2 X 14-inch), with a serrated pizza cutter or knife.
Spread the apple filling on the pastry up to 2.5-cm (1-inch) of the rim. Brush the perimeter of the pastry with water.
Place, diagonally, 6 strips of dough side by side, spacing them equally over the filling. Gently squeeze the strips around the perimeter. Repeat with remaining strips in the opposite direction.
Brush the strips with melted butter. With the pizza cutter or knife, cut around the pastry to remove any excess dough. Sprinkle with the sugar.
Bake for 30 minutes or until the pastry is golden brown.
Serve warm or cold with crème fraîche or vanilla ice cream.
Variation Add cinnamon to the filling, to taste.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.