Pour heavy cream into a food processor* and blend until the cream breaks and you start to see pieces of butter separating from the liquid. This typically takes 5-10 minutes.
Drain the butter from the liquid using a cheesecloth or fine mesh strainer. The liquid is buttermilk, so don't throw it out! Instead, pour it into a separate container and save it for baking.
Transfer the butter to a clean bowl and pour over cold water. Rinse and press the remaining buttermilk out of the butter using a wooden spoon or silicone spatula.
Pour off the water and repeat the process until the water runs clear. (3-4 times in total)
After rinsing, make sure to squeeze out all remaining water from the butter.
Lastly, mix in salt to taste. You can also add different flavorings, like garlic, herbs, or honey if you prefer.
Scoop into an airtight container, and voilĂ ! You've got homemade butter.
Notes
*you can also use a hand mixer or stand mixer to blend the cream.The butter should have a classic butter consistency. If it's looking/tasting a little watery, make sure you squeeze out all the excess water and buttermilk. You can use your hands to do this if you find that easier.