Heat the oil in a large skillet over medium-high heat. Add the onion and cook, stirring occasionally, until soft and translucent, about 5 minutes. Add the garlic and jalapeño and cook for another minute. Add the sweet potato and curry powder and cook, stirring occasionally, for another 5 minutes. Add the tomatoes, Sunbutter, chicken broth, and cayenne. Bring to a boil, stirring occasionally. Cover the pan, lower the heat and simmer for 20 minutes or until the sweet potatoes are tender. Taste and season with salt and pepper. Add the turkey, cover the pan and cook until the chicken is heated through, about 5 minutes. Stir in the spinach and serve hot over rice, if desired.