In large bowl, beat butter with electric mixer on medium-high speed 30 seconds or until fluffy. On low speed, beat in 1 cup of the powdered sugar until incorporated, scraping down sides of bowl occasionally. In 3 portions, add cooled caramel, beating well after each addition. Add remaining 1 cup powdered sugar; beat until incorporated and frosting is fluffy. Beat in 1/4 teaspoon of the kosher salt; taste. Repeat adding 1/4 teaspoon kosher salt at a time until desired saltiness is reached.