Combine flour, sugar, and salt in a large bowl.

Add the margarine and use your fingers to work it into the mixture until the mixture resembles coarse crumbs.

Add the water, working it in until a dough is formed. Shape the dough into a ball, cover with plastic wrap, and refrigerate for one hour.

In a medium-sized bowl, combine the plums, sugar, cornstarch, lemon juice, zest, and vanilla sugar and toss to combine. Set aside.

Preheat oven to 425 degrees Fahrenheit (220 degrees Celsius).

Remove dough from the refrigerator. Prepare two sheets of Gefen Parchment Paper. Lightly flour one sheet. Place the dough disc on top. Place the second sheet on top of the dough. Roll out the dough to a 12-inch (30-centimeter) circle. Transfer the rolled-out dough and parchment sheets onto a baking sheet. Remove the top piece of parchment and discard.

Melt the raspberry preserves. Smear half of the preserves onto the dough, leaving a two-inch (five-centimeter) border all around. Working from the outer part of the circle, lay the plum wedges on the preserves, slightly overlapping the slices. Work inward until the plums are finished.

Using the parchment paper, gently fold up the dough around the border, pleating as needed and pressing down lightly to secure up and over the fruit.

Brush the crust with water and sprinkle with a little turbinado sugar or additional white sugar.

Bake for 35–40 minutes. Remove from oven. Brush remaining raspberry preserves over the plum wedges. Allow to cool before serving.