Melt the sugar in a heavy bottomed saucepan stirring constantly and watching carefully to make sure it does not burn. Sugar will turn into an amber colored substance at this point.
Once sugar is completely melted, immediately add the butter. Be careful in this step because the caramel will bubble rapidly when the butter is added.
Stir the butter into the caramel until it is completely melted, about 2 minutes. If you notice the butter separating or if the sugar clumped up, remove from heat and stir quickly to combine it again. I wear gloves and use a splatter screen at this step. Keep whisking until it comes back together, even if it takes 3-4 minutes. It will eventually– just keep whisking. Return to heat when it’s combined again.)
Very slowly drizzle in 1/2 cup of heavy cream while stirring. Since the heavy cream is colder than the caramel, the mixture will rapidly bubble when added. Allow the mixture to boil for 1 minute. It will rise in the pan as it boils. Watch that it does not boil over.
Remove from heat and stir in 1 teaspoon of salt. Allow to slightly cool down before using. Caramel thickens as it cools.
Cover tightly and store for up to 1 month in the refrigerator. Caramel will thicken in the refrigerator. You can reheat in the microwave or on the stove to desired consistency.