Preheat oven to 400F.
Place the sweetpotatoes on a baking sheet lined with foil or parchment paper.
Bake for 45 minutes or until the sweetpotatoes are tender enough to pierce with a fork.
Once the sweetpotatoes are almost done cooking, heat a large skillet over medium heat.
Add the chicken breast and brown on all sides, about 2 minutes per side.
Season the chicken with the fajita seasoning while it is cooking.
Add the onions, and bell peppers into the skillet and cook until softened.
Once the sweetpotatoes are done, slice them open and top them with the fajita mixture.
Top with sour cream and cilantro, if desired.