Combine in sauce pan oil, sweet potato, and onion and cook over medium-high heat.
Stir and cook until sweet potato start to soften, then stir in the garlic, chili powder, cumin and salt.
Add the water, reduce heat to low, cover and simmer for about 10 minutes or until the sweet potatoes are soft.
Add the beans, tomatoes, and lime juice, stir and simmering about 10 minutes just until heated through.
Serve with Sour Cream and Cilantro.