Heat the oil over medium high heat in a heavy, deep pot. Add the onion, turkey, 1 tablespoon chili powder, and 1 tablespoon taco seasoning. Add water as needed to keep the turkey moist and moving around in the pan. When the turkey is browned and crumbled and the onions are soft, remove from the pan and set aside.Add the sweet potatoes to the same pot with the remaining spices and stir to combine. When the sweet potatoes have browned just slightly, add the garlic, water, and broth. Bring to a low boil and simmer for 10 minutes or so, until the sweet potatoes are very soft. Using an immersion blender, puree the mixture until it reaches your desired consistency (you can also transfer to a regular blender and puree that way).Add the browned turkey, black beans, and cayenne - stir to combine.