Spicy Sweet Potato Soup

INGREDIENTS

• 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