In the bowl of a stand mixer fitted with the whisk attachment, beat butter at medium-low speed until smooth and creamy, stopping to scrape sides of bowl. Beat in zest and salt.
With mixer on low speed, beat in confectioners’ sugar, 1 cup at a time, until well combined, stopping to scrape sides of bowl. Increase speed to medium; beat in juice and milk until thick and smooth. Use immediately.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/sweet-tea-lemonade-cake/