Beat the softened butter on medium speed using an electric mixer for about 2-3 minutes until it's smooth. Add the lime zest and fresh lime juice to the butter and continue mixing until well combined. Gradually add the powdered sugar, 1 cup at a time, beating on low speed. Once all the powdered sugar is incorporated, turn the mixer speed to medium and beat until smooth and fluffy.
Stir in the vanilla extract and a pinch of salt to balance the sweetness. Beat the frosting on high speed for an additional 2-3 minutes until it’s light and fluffy.