In food processor add the 1 1/4 cups of flour, 2 tablesppons sugar and salt - pulse to mix completly. Add butter and pulse to incorperate to resemble a course pea sized mixture. Add cold water slowly and pulse until the dough comes together. (do not over mix) Gather the dough and pat into a rounnd ball wrap in cling wrap and refridgerate for approxiamtely 30 minutes to an an hour.
Preheat the oven to 425 degrees position the rack to the thrid level - line the baking sheet with parchment paper. Working on a lightly floured surface roll out the dough into a disk shape to approximately 12 inches in diameter, transfer to the baking sheet and chill for another 15 to 30 minutes.
In a bowl combine the remaining regular sugar plus 2 tablespoons (sugar not raw sugar) with cornstartch, cinnamon and organge zest. Add the plums and toss well. Let the mixture stand stirring every 5 mins or so to release the sugars from the plums for apporximately 15 to 20 minutes or until sugar is dissolved.
Arrange the fruit in a circular fashion around the dough working into the center making sure to leave a good 1 1/2 inch plus around the outside edges. Fold the dough over onto the plums. Brush the outside rim of dough with the egg yolk whisked with the water - and sprinkle with the raw sugar.
Bake the crostata for approx 50 mins or until center fruit is bubbling and the outside crust is golden brown - let cool on baking sheet for a good 30 to 40 minutes cut in wedges and serve with ice cream or whipped cream.
You can fridgerate the actual dough for up to 3 days.