Put the cranberries and apples in a large mixing bowl; stir to combine.
Stir in the sugar, lemon juice, and flour; set aside for 10 minutes.
Scrape the filling into the chilled pie crust; smooth the top with your hands.
Place pie on the center rack of a 400° oven; bake for 30 minutes.
While the pie is baking, make the topping--in a bowl, combine the flour, sugar, and cinnamon; add in the butter and rub it into the dry ingredients until the mixture resembles coarse crumbs; refrigerate until ready to use.
Take the pie out of the oven and lower oven temperature to 375°.
Sprinkle the crumb topping over the filling and press gently to compact.
Return pie to oven--rotate pie so that the part that faced the back of the oven now faces the front (put a foil-lined baking sheet onto the rack below to catch any spills).
Bake for 25-30 minutes or until the topping is golden brown and the juices bubble thickly aroung the edge.
Put pie on a wire rack to cool for at least 1 hour before serving.