For the dough: Combine the flour, salt and butter in a large bowl. Using a bench scraper or pastry cutter, cut the butter into the flour until the butter is pea-sized. Slowly add the ice water, folding it into the flour until a dough comes together, being mindful not to overwork it. (If the dough is too dry, add another tablespoon of ice water at a time.) Turn the dough out onto a lightly floured work surface and form it into a disk. Wrap it in plastic and refrigerate for at least 30 minutes.
Preheat the oven to 375 degrees F.
On a lightly floured work surface, roll the dough out into a 1/8-inch-thick circle. Then roll it up onto the rolling pin and gently lay it out on a parchment-lined baking sheet.
For the filling: In the center of the rolled out dough, add the plums and sprinkle them with the brown sugar, ginger, vanilla, lemon juice, salt, flour and butter. Fold the edges of the dough over to create a rough border; it doesn¿t have to be perfect, just good enough to form a wall. Brush the edges with milk and sprinkle with turbinado sugar.
Bake until the filling is bubbling and thickened, and the crust is golden brown, 45 minutes. Cool slightly before serving.