Roll the pie crust out to about a 12 inch circle. Place it on a parchment lines rimmed baking tray and refrigerate until ready to fill.

Preheat oven to 400 degrees.

Mix together plum, raspberries, sugar, salt, lemon juice, and the cornstarch. Let mixture sit for about 15 minutes to allow juices from the fruit to emerge. Toss to coat fruit.

Mound fruit on the dough round, leaving a 1 1/2-inch border.

Gently fold the pastry over the fruit, pleating to hold it in.

Brush dough with beaten egg and sprinkle raw sugar over dough.

Bake 35-45 minutes, until filling is bubbly and crust is golden brown.

Cool for at least 20 minutes before serving.