500g spaghetti, plus Parmesan or vegetarian cheese, grated, to serve
Heat the oil in a large saucepan and add the onions, carrots, celery and garlic. Cook gently for 15-20 mins until everything is softened. Stir in the lentils, chopped tomatoes, tomato purée, herbs and stock. Bring to a simmer, then cook for 40-50 mins until the lentils are tender and saucy – splash in water if you need. Season.
If eating straight away, keep on a low heat while you cook the spaghetti, following pack instructions. Drain well, divide between pasta bowls or plates, spoon sauce over the top and grate over some cheese. Alternatively, cool the sauce and chill for up to 3 days. Or freeze for up to 3 months. Simply defrost portions overnight at room temperature, then reheat gently to serve.