5
In another small bowl, beat softened butter with electric mixer on medium speed until fluffy. Add melted caramel mixture; beat until well blended. On low speed, beat in 1/2 cup of the powdered sugar until smooth, scraping down side of bowl occasionally. Add remaining 1/2 cup powdered sugar; beat until smooth and frosting is fluffy. Beat in 1/8 teaspoon kosher salt.