Put the sugar in a small saucepan and let it melt without stirring until it turns slightly golden. Then let it melt briefly while stirring. Then add the butter piece by piece. Attention! It steams and foams! When all the butter has melted add the salt. Keep stirring. Then slowly add the cream and simmer for another minute.
Put it in a middle screw jar while still hot and let it cool down.
The sauce will keep in the refrigerator for about 2 to 3 weeks. It can be eaten on bread, warmed up and poured over a New York cheesecake or spooned straight.