It turns out that they can also come from my refrigerator. And they're really easy to make.
5 roasted beets
1/2 cup apple cider vinegar
1/2 cup water
1/2 cup sugar
If you haven't already, roast your beets. [To roast beets, I put them in a glass baking dish with 1 inch of water in it, then cover the dish with aluminum foil, and put it in the oven for an hour at 400 degrees. After an hour, I remove the dish from the oven and set it aside to cool. When the beets are cool enough to handle, I can slip their skins right off, no peeling or washing necessary.]
Slice the roasted beets into circles or chunks (I like circles). Put the sliced beets into a glass bowl or jar. In a separate bowl, mix together the apple cider vinegar, water, and sugar. Pour the mixture over the beets. Make sure all the beets are covered by the liquid, cover the bowl or jar, and put it in the 'fridge for at least 24 hours.
That's it! The salad-bar beets of my childhood memories!
I saw many, many, much more complicated pickling recipes elsewhere on the interwebs. I'm not sure why. This simple recipe does the trick. I wouldn't change a thing.
Admittedly, this recipe uses refined sugar, which is an ingredient I usually try to avoid. However, it's a relatively small amount per serving, and it made me love beets again after I had a bad experience. So I'm okay with it.