Place sugar in a medium saucepan and add water. Moisten all of the sugar to make an even layer.

Cook over medium-low heat, stirring occasionally until the preparation turns clear and the sugar dissolves. This might take several minutes. 

If any sugar crystals form on the sides of the saucepan, lightly dip a pastry brush in water and use it to sweep away sugar crystals without touching the caramel. 

Don’t stir again once it starts to bubble and is clear. Let it cook until it turns amber-colored, swirling the pan occasionally to avoid it burning in spots. Be careful not to burn it. 

When it’s a deep amber, remove from the heat and add the butter in small pieces. Stir to melt completely. 

Add the cream slowly, whisking constantly until it’s fully integrated. 

Add the salt and vanilla. Mix to combine. Don't taste it; you'll burn your mouth. Let it cool first.

Cool in the pan for about 5-10 minutes and then pour into the glass jar you’ll be storing it in. Let cool completely before sealing and refrigerating it for up to a month.