Preheat your oven to 400°F (200°C).
Wash and pierce the sweet potatoes with a fork.
Bake the sweet potatoes for 45-60 minutes, until tender.
While the potatoes bake, prepare the cranberry-apple mixture.
In a saucepan, combine cranberries, diced apple, brown sugar, and a dash of cinnamon.
Simmer until cranberries burst, about 5-7 minutes.
Remove the sweet potatoes from the oven and let cool slightly.
Slice the sweet potatoes in half lengthwise and scoop out the flesh into a bowl, leaving a thin layer attached to the skin.
Mash the sweet potato flesh with butter, milk, cinnamon, nutmeg, and salt.
Fold in the cranberry-apple mixture until well combined.
Spoon the filling back into the sweet potato skins.
Return the stuffed sweet potatoes to the oven and bake for an additional 15-20 minutes.
Remove from the oven and let rest briefly before serving.