In the bowl of a stand mixer, or using an electric mixer, blend the softened butter and cream cheese until the mixture is smooth, creamy, and free of lumps.
Add the vanilla extract and salt to the mixture, stirring thoroughly to combine.
Gradually incorporate the powdered sugar, keeping the mixer on low speed, until the sugar is fully blended into the mixture.
Once the frosting is smooth and fully combined, it is ready to be used to frost your completely cooled cake or cupcakes.