Preheat oven to 350F.
Add the oil and onions to a sauté pan or dutch oven over medium heat. Sauté for 5-6 minutes, or until the onions have softened.
Next, add the ground beef and spices and cook until browned.
Turn off the heat.
Stir in the cranberries, celery, walnuts and sage.
Spoon the mixture into the hollowed apple halves and bake at 350F for 25 minutes, or until the apples are tender.