Heat the olive oil in a large saucepan over medium heat, and cook the onion until tender. Mix in ginger and garlic, and season with cayenne pepper, thyme, allspice, and celery salt. Pour in the broth. Mix in tomato puree, refried black beans, black pepper, and sugar. Cook and stir until heated through.
Mix the remaining black beans and lemon juice into the soup. Continue cooking until heated through. Top each serving with a dollop of sour cream.
