In a covered soup pot, simmer the onions, garlic, chile, and salt in 1 cup of the vegetable stock for about 10 minutes, or until the onions are soft.
In a small bowl, make a paste with the cumin and a tablespoonful of the stock, stir it into the pot, and simmer for another 1 to 2 minutes.
Add the sweet potatoes and the remaining stock and simmer for about 10 minutes, until the sweet potatoes soften. Add the bell pepper and corn and simmer, covered, for another 10 minutes, or until all of the vegetables are tender.
Puree about half of the soup in a food processor and return it to the pot. The soup will be creamy and thick. Add salt to taste and gently reheat on low.