Salted Caramel Sauce

1 cup white sugar
1/4 cup water
3/4 cup heavy cream, room temperature
3 1/2 tablespoons butter
1 teaspoon salt
1/2 teaspoon vanilla

Combine the sugar and water in an even layer in the bottom of a metal pot. Stir over medium-low heat until the sugar starts to dissolve.
Increase the heat to medium-high and stop stirring. Once the sugar mixture starts to boil, you can swirl and shake the pan, but stirring will cause the sugar to crystallize. Continue to boil until the mixture turns a deep amber color, or a candy thermometer reads 350 degrees F. Be sure to watch it carefully, as caramel can go from perfect to burnt in seconds.
Remove the pit from the heat and quickly whisk in the cream. Be careful since the caramel will splatter. You may want to wear an oven mitt.
Whisk in the butter, salt and vanilla. If any clumps form, keep whisking until they melt. Pour the caramel sauce into a glass jar to cool. The sauce needs to be refrigerated and will last for up to 3 weeks.