Chop the Onion into medium size pieces and place into a saucepan. Use non stick Fry the onions until they are soft and translucent then add the carrots Add all the stock and bring to the boil. Turn the heat down to a simmer and add the Lentils, cover with a lid and leave to simmer for 15 minutes. The Lentils will go soft and absorb most of the liquid. Blend the soup in the saucepan with a hand blender and then add any extra liquid (either water or stock) to the thickness you want. Add the tin of tomatoes and carry on blending until you have a smooth orange soup. Serve with your favourite bread