Place the sugar on a pan over medium heat. Let it become a pale golden colour and don't use any tools to mix it. Just use the handle of the pan to swirl it around if needed.
Once golden, add the cream and salt and whisk quickly and vigorously. Be careful here because it will bubble up and it's very hot.
Remove the sauce from the pan. Let it cool down completely. If it thickens too much, you can reheat it and add a splash of boiling water to adjust it. Separate half the caramel sauce for the ice cream, the other half is for serving.