Place cream in the bowl of a food processor, blender, or kitchen-aid mixer. Blend until it separates into buttermilk and clumps of butter that look like fluffy scrambled eggs, then keep whirling until butter forms bigger clumps, about 5 to 10 minutes.
Set a fine strainer over a bowl. Pour milk and butter into strainer and let drain briefly. Squeeze butter with your hands to extract remaining milk.
Place butter in another bowl and sprinkle with salt to taste.