Melt the dairy-free butter in a large heavy-based pan over a medium heat.
Add the chopped onion and cook until soft and translucent.
Add the crushed garlic and cook for 1 minute.
Pour in the vegetable stock.
Add the sliced carrots and red lentils, bring to the boil, then reduce to a gentle simmer.
Simmer until the carrots and lentils are soft, stirring occasionally to prevent the lentils from sticking.
Season with salt and freshly ground black pepper.
Add the chopped coriander stalks and leaves towards the end of cooking.
Blend the soup using a hand-held blender until smooth.
Taste and adjust seasoning if needed.
Serve hot.