Put the 2 tbsp of oil in to a pan and heat up then add the onions and fry. Add all the other ingredients (flour being last) then add in the water. Cover with the lid and let the soup cook until the lentils and carrots are soft.
Transfer the soup to a blender and wiz until smooth then transfer back to the pan. I have made this soup quite thick (which is the way I like it) but if you want a more "runny" soup then add some more hot water (adjust to your taste).
Transfer to a bowl and sprinkle paprika over the top. However you can make a sauce of 2 tbsp of butter and 1 tbsp of red pepper (powder), mix the two ingredients in a saucepan and then pour over the soup