Add your heavy cream to a bowl or the bowl of your stand mixer.
Beat on low speed then increase to medium as the cream thickens and makes less of a splash.
You'll notice the cream will turn to whipped cream. Keep beating past this step to make butter.
The cream will then separate into a liquid and chunky solids. The liquid is your buttermilk. The solids are the butter.
Strain the everything over a bowl to catch the buttermilk if you plan on keeping it.
While the butter is still in the strainer, rinse it with cold water while stirring it. This will remove any excess buttermilk and give you a longer shelf-life for you butter.
You can now add in the salt, or any other seasonings you'd like!