Apple Custard Pie with Cinnamon Streusel

Prepare our Basic Pie Pastry. Adjust oven rack to lower third of oven. Heat oven to 425 degrees F. Cinnamon Streusel: In a small bowl, combine brown sugar, flour, butter, and cinnamon. Using hands, mix until large crumbs form. Stir in walnuts. Filling: In a bowl, whisk sugar, flour, and salt. Add sour cream, egg yolks, vanilla, and lemon zest; whisk until smooth. Sprinkle bottom of unbaked pie shell with dried cranberries. Arrange apple slices in a concentric circle over cranberries. Pour sour cream mixture over apples. Sprinkle streusel on top. Bake 15 minutes. Reduce oven temperature to 350 degrees F. Bake 45 to 50 minutes longer, or until apples are tender and custard is set. Cool completely on a wire rack.