Heat granulated sugar in a medium saucepan over medium heat, stirring constantly with a wooden spoon. Sugar will form clumps & eventually melt into a thick amber colored liquid. Be careful to not burn it.
Once sugar is completely melted, add the butter immediately. Stir with a whisk until the butter is completely melted.
Slowly drizzle in the heavy cream while stirring. Allow the mixture to boil for 1 minute.
Remove from heat and stir in the salt. Allow to cool before using.
Make ahead: You can make this caramel in advance. Keep it covered tightly & store for up to 2 weeks in the fridge. Warm the caramel for a few seconds in the microwave before using.