In a large mixing bowl, beat the softened cream cheese and butter together with an electric mixer on medium speed until light and fluffy, about 3 minutes.
Add the powdered sweetener, vanilla extract, and salt. Beat on low speed for 30 seconds to prevent a sweetener cloud in your kitchen.
Increase speed to medium-high and beat for 3-4 minutes until the frosting is smooth, creamy, and well-combined.
If the frosting is too thick for spreading or piping, add heavy cream one tablespoon at a time, beating well after each addition, until you reach your desired consistency.
Use immediately to frost cooled cakes or cupcakes, or store in an airtight container in the refrigerator for up to 5 days.
If refrigerated, let the frosting come to room temperature and re-whip for 1-2 minutes before using.