Heat the sugar at medium heat in a saucepan. A big one is preferred. Let it melt without touching it as you then avoid lumps. Once the sugar has dissolved, remove the pot from the heat.
Immediately add the butter in smaller portions and with continuous stirring in the mass.
Put the saucepan back on the heat and immediately add the cream while still stirring in the caramel mass.
When the sauce has become smooth and thick remove it from the heat and add a well-dried salt (taste yourself - make sure you do not burn yourself!).
If the caramel sauce is too thin you can cook it a little more, if it has become too thick add a little more cream.