Preheat your oven to 350°F (175°C). Lightly grease your 9×13 inch baking dish with non-stick cooking spray or a thin layer of butter.
In a medium mixing bowl, toss the cranberries with the granulated sugar, orange zest, and orange juice until the berries are evenly coated.
Spread the cranberry mixture in an even layer across the bottom of the prepared baking dish.
Sprinkle the dry cake mix evenly over the fruit layer. Do not stir the mixture; leave the cake mix as a loose, powdery layer on top.
Place the thin pats of butter across the surface of the cake mix, ensuring as much of the dry powder is covered as possible to avoid dry spots.
Sprinkle the optional chopped nuts over the top of the butter.
Bake for 30 to 35 minutes, or until the top is golden brown and the fruit juices are bubbling around the edges.
Remove from the oven and let the dish rest for at least 10 minutes before serving, allowing the juices to thicken slightly.