Combine flour and salt in a bowl. Mash shortening into the flour mixture with a pastry cutter or fork until the mixture is crumbly. Gradually add cold water as needed, tossing with a fork until dough forms a ball. Wrap dough in plastic wrap and refrigerate for 30 minutes.
Turn dough out onto a flat work surface dusted with flour. Divide dough in half and form each half into a ball.
Roll dough ball from center to edges into a circle 2 inches larger than the pie plate and about 1/8 inch thick. Wrap dough around rolling pin, starting on one side of the circle. Unroll over pie plate and trim dough.
Roll remaining dough ball into a crust to fit the top of the pie and set aside.
Beat egg white and 1 tablespoon water; brush over bottom of crust and set aside.
Combine 3/4 cup sugar, cornstarch, lemon peel, vanilla extract, and cinnamon in a bowl. Gently stir blueberries and raspberries into the mixture to coat; pour into the crust. Top with reserved pie crust.
Brush top of pie crust with 1 tablespoon water; sprinkle 1 tablespoon sugar over the moistened top.
Cut a few slits into top crust with a sharp knife.
Bake in preheated oven until crust is golden brown and filling is bubbly, about 45 minutes. Set pie onto wire rack to cool completely before refrigerating.
