In a medium cast iron skillet over medium to medium-low heat, heat avocado oil.
Add onion, apples, and cinnamon. Cook until soft, about 7 minutes.
Remove from pan and add sweet potatoes and carrots (add more oil if needed). Cook undisturbed for 2-3 minutes.
Stir, allow to cook for another 2-3 minutes undisturbed.
Continue cooking sweet potatoes, stirring as needed to insure all sides get browned and none burn, until soft (about 5-6 more minutes, about 12 minutes total).
Add reserved onion and apples back to pan. Add spices and stir to combine and warm throughout. Serve.