Combine the berries with the sugar, cornstarch, and lemon zest. Set aside.
In a food processor fitted with a metal blade, combine the flour, salt, sugar, and chilled butter. Pulse the processor until butter is incorporated and pea-sized.
Combine the egg and water and add to the processor while running. Once the dough forms, stop the processor. Gather the dough into a ball and wrap in plastic wrap. Chill, but only for 1 hour or it will be too difficult to roll out.
Preheat oven to 400º F.
Flatten the dough slightly and roll it out on a floured board to a 1/4 inch (or slightly less) thickness. (Don't worry about the edges being rough; that is part of the look of the tart.) Remove the dough to a parchment-covered baking sheet.
Fill the center of the tart with the raspberry mixture and fold the sides up over the filling. If desired, brush on some beaten egg and sprinkle with sparkle sugar.
Bake for 30 minutes or until tart is golden brown and the filling is bubbly. Cool for at least 15 minutes before cutting into four sections for serving.