Soak the lentils overnight. Put the lentils in a saucepan with a large amount of water. Boil for 45 minutes on a medium heat.

Melt the butter in another saucepan. Brown the onion in it for 3 minutes. Add the meat and cook it for 3 or 4 minutes with the onion. Add the tomato sauce and stir. Finally add the broth, salt and lentils and cook on a very low heat for 1 and 1/2 hours.