This recipe is so much better than anything in a jar.
In a medium deep saucepan, stir the sugar and 2 tbsp. water over medium heat until the sugar dissolves, about 3 minutes. Increase heat to high. Bring to a boil. Without stirring, swirl the pan occasionally and brush down the sides of the pan with a wet pastry brush until the sugar turns deep amber, 6 to 8 minutes. Remove from heat. Add the cream, butter, and salt. (The mixture will bubble up vigorously.) Stir until the butter melts. Let cool.