Preheat oven to 350. Lightly grease a 10-inch skillet or pie pan.

Let pie dough stand at room temperature for 10 minutes. On a lightly floured surface, roll one pie crust into a 14 inch circle. Repeat with second pie crust.

Brush one pie crust with water and lightly brush with water. Place the second crust on top. Transfer to prepared pan, pressing into bottom and up the sides. Crimp edges as desired.

Layer blackberries in prepared crust. Arrange peaches over blackberries. Place the pie on a rimmed baking sheet.

In a medium bowl, whisk together sugar, flour and salt. Mix in buttermilk, eggs and vanilla. Stir in melted butter. Carefully pour over fruit.

Bake for 55-65 minutes, or until center is golden brown and set. Cool completely on a wire rack before slicing and serving.