In a medium saucepan cook onions and carrots in olive oil over medium heat for 5 minutes.
Stir in curry powder; cook 1 minute more. Add chicken broth and cayenne pepper. Bring to boiling; reduce heat and simmer, covered for 5 minutes.
Stir in orange juice and mashed, cooked sweet potato; heat through.
With an immersion blender, puree to desired consistency. Add salt to taste. Top each serving with purchased croutons, plain yogurt and snipped fresh cilantro, if desired.