Using a large pot (taller is better-to help minimize the chances of burning yourself. Wearing long sleeves is also a good idea in the event of spattering) heat the raw sugar over medium-high heat.
Whisk occasionally until the sugar starts to melt, then whisk constantly until it is all melted and (fairly) smooth.
Carefully add the butter and whisk until smooth and combined.
Remove from heat and slowly add in the cream, whisking as you do so.
Add in the sea salt and whisk until everything is evenly incorporated and it is fairly smooth. The caramel should be a dark amber color.
Carefully pour the caramel sauce into a heatproof container (such as a glass jar) and allow to cool completely at room temperature (the container will be hot for awhile due to the caramel sauce, so use caution).
Store in the refrigerator (in an airtight container) for up to 2 weeks.