Preheat the oven to 400°F (200°C). Scrub the sweet potatoes clean, then pierce each a few times with a fork. Place them on a baking sheet and bake until tender, about 45 minutes to 1 hour, depending on their size.
While the potatoes bake, heat a large skillet over medium-high heat. Add the diced onion and a pinch of salt. Cook until the onion is soft and translucent, about 3–4 minutes.
Push aside the onions, add the ground turkey to the skillet, and break it up with a spoon. Cook until it’s no longer pink, about 5–7 minutes.
Stir in the garlic, chili powder, cumin, paprika, and a pinch of salt and pepper. Let the spices bloom for about 30 seconds, until fragrant.
Add the black beans and corn to the skillet. If you’re using thawed frozen corn, give it a quick stir to heat through. Reduce the heat to medium and simmer for 5 minutes to meld the flavors.
When the sweet potatoes are done, remove them from the oven. Allow them to cool just enough to handle, then slice each one open lengthwise and gently press the ends to fluff the insides.
Spoon generous portions of the turkey chili into each potato shell. Top with shredded cheddar. Return the stuffed potatoes to the oven for 5–7 minutes, or until the cheese is melted and bubbling.
Serve warm with optional toppings: a dollop of sour cream, a squeeze of lime, and a handful of chopped cilantro or scallions.