Heat the oil in a large pot over medium heat. Add the onion and garlic, and cook until softened.
Stir in the red curry paste and cook for another minute.
Add the butternut squash, coconut milk, and vegetable broth. Bring to a boil, then reduce heat and simmer until the squash is tender, about 20 minutes.
Stir in the soy sauce and lime juice. Adjust seasoning to taste.