Preheat the oven to 400°F (200°C).
In a large skillet, heat olive oil over medium heat. Add onions and garlic, sautéing until softened.
Add the ground turkey to the skillet, cooking until browned and no longer pink, about 5-7 minutes.
Stir in diced sweet potatoes, bell peppers, paprika, oregano, salt, and pepper. Mix well.
Transfer the mixture into a baking dish, spreading it evenly.
Cover the dish with aluminum foil and bake for about 30 minutes.
Remove the foil, sprinkle cheese on top if using, and bake uncovered for an additional 15 minutes.
Check for doneness; sweet potatoes should be tender. Remove from the oven and let it cool slightly before serving.