Preheat your oven to 400°F (200°C). Pierce each sweet potato several times with a fork, then rub the outsides with 1 tablespoon of olive oil. Place them directly on the oven rack and bake for 45-60 minutes, or until they are very tender when pierced with a knife.
Meanwhile, in a small bowl, combine the chili powder, cumin, smoked paprika, garlic powder, onion powder, black pepper, and ½ teaspoon of salt to create a fajita seasoning blend.
Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the sliced bell pepper and onion and cook for 5-7 minutes, stirring occasionally, until the vegetables are tender and lightly charred. Transfer the vegetables to a bowl and set aside.
Add the remaining 2 tablespoons of olive oil to the same skillet. Add the chicken strips and the prepared fajita seasoning. Cook for 6-8 minutes, stirring often, until the chicken is fully cooked through and no longer pink. Stir the cooked vegetables back into the skillet with the chicken and the remaining ½ teaspoon of salt, then remove from heat.
Once the sweet potatoes are cool enough to handle, slice them in half lengthwise. Carefully scoop out the inner flesh into a large bowl, leaving a ¼-inch thick shell so the potato skins hold their shape.
Add the chicken and vegetable mixture, sour cream, and half of the shredded cheese to the bowl with the sweet potato flesh. Gently mash and stir everything together until well combined.
Evenly divide the filling among the 8 sweet potato skin shells. Top with the remaining shredded cheese. Arrange the filled potatoes on a baking sheet and bake for 15-20 minutes at 400°F (200°C), until the cheese is melted and bubbly and the filling is heated through.
Remove the potatoes from the oven and let them cool for 5 minutes. Garnish with chopped fresh cilantro before serving.