1. Preheat oven to 375° F. To make the filling, combine peaches and blackberries in a large bowl. In a small bowl, whisk together 3/4 cup sugar, flour, cornstarch and cinnamon. Pour sugar mixture over the fruit. Gently toss together with a spatula. Stir in the lemon juice.  
2. On a floured work surface, roll out pie dough to a 14-inch circle. Turn and flour the dough as you roll to keep it from sticking. Wrap the dough around the rolling pin. Carefully unroll over a 9-inch pie plate. Cut off excess dough. Press the dough edges around the rim of the pie plate. Pour the fruit mixture onto the pie dough. Sprinkle the top with remaining sugar. Bake for 55 to 65 minutes. If crust begins to darken, cover the edges with foil. Remove from oven, and let cool completely before serving.
3. Note: If desired, top the pie with a decorative pie crust or lattice. Brush with egg wash, and sprinkle with sugar before baking. 

Calories: 317, Fat: 12 g (7 g Saturated Fat), Cholesterol: 30 mg, Sodium: 1 mg, Carbohydrates: 50 g, Fiber: 4 g, Protein: 4 g.