Start by thoroughly washing the beets under running water to remove any dirt.
Cut off the tops and tails of the beets, leaving about an inch of the stems intact (this helps prevent bleeding during cooking).
Place the beets in a large pot and fill with enough water to cover them.
Bring the water to a boil, then reduce to a simmer. Cook the beets for 45–60 minutes, or until tender when pierced with a fork.
Once the beets are cooked, drain the pot and allow the beets to cool slightly.
When cool enough to handle, rub the skins off the beets using your hands or a paper towel. The skins should come off easily.
Slice the beets into ¼-inch thick rounds or cubes, depending on your preference.
In a medium saucepan, combine the apple cider vinegar, water, sugar, salt, black peppercorns, bay leaf, and cloves (if using).
Bring the mixture to a simmer, stirring until the sugar and salt are fully dissolved. Remove the brine from heat.
Place the sliced beets and onions (if using) into a sterilized quart-sized jar.
Pour the hot brine over the beets, ensuring they are fully submerged.
Let the jar cool slightly before sealing it with a lid.
Refrigerate and WaitOnce sealed, refrigerate the jar of pickled beets for at least 24 hours to allow the flavors to meld. The beets can be stored in the refrigerator for up to 4 weeks.