In a large soup pot or saucepan, saute the onion in oil over medium high heat for 10-15 minutes or until onion is golden.
Stir in curry powder and cayenne.
Add the broth and chard and increase heat to high and bring to a boil.
Reduce heat to medium and stir in lentils and garbanzos. Cover pan and simmer for 10 minutes or until lentils are tender (if you use brown lentils it will take longer for lentils to be tender), stirring occasionally.
Divide soup into bowls and top with sour cream or yogurt, if desired.