Wash sweet potatoes and carrots thoroughly, peel them, and cut into cubes.
Finely chop the onion.
Heat olive oil in a pot and sauté the onion until translucent.
Add the sweet potatoes and carrots, and stir-fry for another 2–3 minutes.
Pour in enough water to cover the vegetables and simmer over medium heat until the vegetables are tender.
Transfer both the vegetables and the broth to a blender and puree until smooth.
Season with salt and black pepper, reheat if needed, and serve in a bowl.