Place pie pastry in 9-inch pie plate. Heat oven to 450F.
To make streusel, place flour cornmeal, sugars and cinnamon in a bowl (or if you already used the processor for the pie crust, it will do quick job of the streusel, too). Add cold butter in small pieces and work with hands until coarse crumbs form.
In a large bowl, combine apples, lemon juice, sugar, flour cinnamon and nutmeg. Pile apple mixture into (uncooked) pie crust. Pat streusel over apples. Bake for 15 minutes. Reduce oven temperature to 375F and bake 45 minutes or until pie is bubbly and apples are tender. Cool. 10 servings.