In standing mixer fitted with the whisk attachment, beat butter at medium-high speed until smooth, about 20 seconds. NOTE: if using a hand-held mixer, increase mixing times by at least 50%.
Add powdered sugar and salt, and beat at medium-low speed until most of the sugar is moistened, about 45 seconds.
Scrape down bowl and beat at medium speed until mixture is fully combined, about 15 seconds; scrape bowl, add vanilla extract and heavy cream, and beat at medium speed until incorporated, about 10 seconds.
Increase speed to medium-high and beat until light and fluffy, about 4 minutes, scraping down bowl once or twice.
Tint frosting with gel food coloring, if desired. Use immediately or store in refrigerator. If refrigerated, allow frosting to come to room temperature before use.