In a large mixing bowl, beat the softened cream cheese and unsalted butter together with an electric mixer on medium speed until smooth and creamy, about 2 minutes.
Add the mashed ripe banana, vanilla extract, and salt to the bowl. Mix on low speed until fully incorporated.
Gradually add the sifted powdered sugar, about 1/4 cup at a time, mixing on low speed after each addition until the frosting is smooth and spreadable.
Increase the mixer speed to medium and beat the frosting for an additional 1-2 minutes to make it light and fluffy.
Use immediately to frost your banana cake or refrigerate in an airtight container for up to 3 days. Bring to room temperature and rewhip before using if chilled.