Melt the coconut oil in a saucepan. Add the diced onion and soften for around 5 minutes.
Add the butternut squash, sweet potato and cumin and stir well. Season with salt and pepper to taste. Cook for another 10 minutes to soften the vegetables, stirring occasionally.
Add the stock and bring to a boil. Turn down the heat and simmer for around 20 minutes or until the vegetables are very soft. Taste and add more seasoning if desired.
Remove from the heat. Using a stick blender, blend the soup mixture to a smooth consistency. If the mixture is too thick, add more water until desired thickness is achieved.