In a heavy-bottomed large pot, combine sugar and water.
Put heat on medium high and let sugar melt.
Stir to help sugar along.
Once dissolved, stop stirring and let it come to a boil.
Boil until the sugar is dark amber in color and swirl pot now and again to help it cook evenly.
Once the sugar is amber add the butter and stir to melt it.
Remove heat and slowly/carefully pour in the cream.
Keep stirring until smooth.
Pour in a glass measuring cup or jar to let cool.
Add salt if using.
Let cool to room temp.