
In a dry, medium-sized stainless steel saucepan or pot, cook the sugar over medium heat.
Swirl the pan occasionally, until the sugar melts and begins to turn a deep golden color, about 5 to 6 minutes.
Turn off the heat and whisk in the butter until melted.
Whisking constantly, gradually add the cream. Whisk until the mixture is smooth. If the caramel seizes or clumps of sugar form, continue heating on low heat until they melt back into a smooth sauce.
Remove from heat and pour through a fine mesh strainer into a heatproof container.
Stir in the salt (if using).
Let hot caramel cool until warm and thick. Use or store in an airtight container in the fridge for up to 2 weeks.