In a food processor, pulse the softened butter and cream cheese together until combined.
Add 1 cup of the sugar and pulse. Repeat until all the sugar is used.
While pulsing, drizzle in the vanilla extract and salt.
Frost your cupcakes.
** If you don’t have a food processor, you could use a traditional stand mixer, electric hand mixer, a plain ol’ wire whisk (a sturdy one), or a fork or spoon. Just expect to put more muscle into it if mixing by hand, and note that it will take a bit longer to blend everything together smoothly.