Don’t toss that rind! You could be making this instead!
7 cups watermelon rind, trimmed and sliced (the rind of about 1 medium watermelon)
about 4 cups Fir Vinegar or apple cider vinegar (or another mild, aromatic herbal vinegar)
about 2 cups sugar
1 teaspoon salt
Eat up a fat watermelon, preferably a crunchy one with a fairly thick, dense rind. Scrape the rind of almost all the pale pink flesh that’s left. Next, in order to slice off the outer rind, use a sharp knife. I like a 7” long, thin-bladed one, as a bigger knife feels more clumsy to me for this particular job. We find it easiest to cut it into small wedges (about 3”x 4”), and then lay each piece on its side, but do it whatever way feels best to you.
After all the outer rind is removed, we slice up the remaining rind into strips about 3” long and 1/4” wide. We measure the pieces using a quart jar, as it’s a lot easier than a measuring cup. (Remember, it’s 4 cups all the way to the rim of the jar.) Put the rind pieces in a pot, and cover with a mixture of apple cider vinegar (or your favorite herbal vinegar) and sugar, 2 parts vinegar to 1 part sugar (or honey). Add 1/2 teaspoon salt for every 2 cups of vinegar. Put the pot over a medium flame, cover the pot, and bring to a boil. Uncover the pot, (this is important in order to get a firm but chewy texture) and simmer over a low flame until the rind is done to your liking.
I like to simmer it until the liquid has almost completely cooked into the rind. Sometimes I do this over more than one day. If the cooking is interrupted the first day, I just leave the pickle-in-progress in the pot and start it again the next day. It will be fine kept at room temperature for a day or two even in the summertime, because of the large amounts of vinegar and sugar, but I would keep the pot out of the sun.
If you want to can it, be sure to squish the candied/pickled rind down completely when filling the jars. This ensures that there are no air pockets and that the small amount of liquid left in the pickle will just cover the rind, once the jar is full. If there is not quite enough liquid to cover the rind when pressed, stir in a bit of boiling water to each jar.
The longer the rind cooks, the more it gets chewy like candy. With a rind that is not particularly dense or crisp, however, it may go through a stage which it seems a little uninteresting in texture. If this happens, persevere, keep cooking until the liquid is gone, and you will be well rewarded for your patience.