Heat the coconut oil in a large pot over medium heat. Add the onion and cook until it softens and turns translucent.
Stir in the garlic, ginger, and bruised lemongrass. Cook for about one minute until the mixture smells fragrant.
Add the red curry paste and stir for 30 seconds to coat the aromatics.
Add the cubed root vegetables, coconut milk, and vegetable broth. Bring everything to a gentle simmer.
Cook uncovered for 20 minutes, stirring occasionally, until the root vegetables are tender when pierced with a fork.
Remove the lemongrass stalks. Stir in the lime juice and add salt to taste.
Ladle into bowls and top with fresh cilantro leaves and sliced red chili.