Heat the oil in a large saucepan and fry the onion and garlic gently for 5 minutes to soften.
Add the cumin and carrot, stir well and fry for 2 more minutes.
Stir in the red lentils.
Add the stock, bring to the boil and simmer for about 20 minutes, until the carrot and lentils are cooked.
Season with black pepper and the lemon juice just before serving.
If you have fresh coriander, serve it to sprinkle on top.