With an electric mixer, beat butter on medium for 1 minute.
Add salted caramel sauce. and vanilla extract, and beat on medium for 2 minutes, scraping down the sides as needed.
Add powdered sugar and salt, and beat on low until powdered sugar is incorporated.
Increase speed to medium, and beat until smooth and well-combined, about 2-3 additional minutes.
Notes
Butter: I like to use salted butter in this recipe. You can use unsalted butter and adjust the salt level with salt as needed.
Caramel sauce: Here is the recipe to make salted caramel sauce. If you would like to use a jarred caramel, make sure you get a thicker sauce and not a thinner topping.
Salt: Also, add a pinch or two of a finishing salt for the "salted" flavor!