1/2 cup sour cream
1 teaspoon grated lime zest
2 large sweet potatoes, peeled and cubed
1 tablespoon butter
1 onion, sliced
2 cloves garlic, sliced
4 cups chicken stock
1/2 teaspoon ground cumin
1/4 teaspoon crushed red pepper flakes
2 tablespoons grated fresh ginger root
1/4 cup smooth peanut butter
1 lime, juiced
2 tablespoons chopped fresh cilantro
salt to taste
1 large roma (plum) tomato, seeded and diced