1. In a food processor with a metal blade or a blender container, combine the beans, broth, salsa, and cumin. Process 1 minute, or until smooth. 2. Heat bean mixture in a medium saucepan over medium heat, until thoroughly heated. 3. To serve, ladle soup into 2 individual bowls. Spoon 1 tablespoon of sour cream on top of each; swirl gently. Sprinkle with green onions.