Add the sugar to a saucepan and let it melt on medium heat, stirring occasionally using a silicon spatula, for about 15 minutes.
Once the sugar is fully melted, add the butter and whisk until melted.
Pour in the cream while whisking. Be careful, it will foam up. Stir for about a minute for sauce consistency. It should be smooth, with no lumps or separation. The longer you cook it the thicker it will get. Remember, it thickens more as it cools.
When ready, remove from the stove, add the vanilla and salt, and continue whisking for 30-60 seconds, then transfer to a jar or use as needed.
Keep it well-sealed at room temperature for a day, or once it’s completely cooked, you can keep it in the fridge for up to 2 months.