Pour the cream into a food processor and blend until the butter separates from the milk.
Pour off the liquid buttermilk from the butter.
Remove the food processor blade and pour enough cold water over the butter to fully cover it.
Use a spatula to stir and smash the water into the butter to rinse off access buttermilk, and then pour off the water.
Repeat steps 3 and 4 until the water is mostly clear when stirred into the butter.
Place the blade back in the food processor, add salt if you would like, and turn it on for a few seconds to form the butter into a ball. (If you added salt, you'll need to let the food processor run a little longer to make sure it's thoroughly mixed.)
Scoop the butter into a cheesecloth and squeeze out any remaining liquid.
Enjoy your homemade raw butter!