This recipe is a 2 step process. Mix all of the ingredients together and let them sit (to macerate) for as few as 2 hours, or even overnight. Letting these ingredients macerate draws the juices out of the rhubarb and tightens up it's texture, which is a good thing when you're going to cook it, or it might get mushy. All those juices blend with the sugar to create a sumptuous syrup.
Note: You can use between 1 and 2 cups of sugar, but I use 2 cups cuz I love this preserve for what it is, both sweet AND tart!)
Makes ~one pint, but I prefer to put it up in 4 - 4 oz. jars
1.) Prepare canning jars and keep hot until ready to use; prepare lids according to the manufacturer's instructions. (If macerating the fruit & sugar mixture overnight, you will want to wait until the next day to prepare the jars.)
2.) Place rhubarb chunks in a large bowl, then zest entire grapefruit over the rhubarb chunks. Next slice the grapefruit in half and squeeze every last drop of juice over the rhubarb/zest mixture.
3.) Add desired amount of sugar, stir together until well mixed, cover, then place the bowl in the refrigerator for a couple hours (or even overnight.)
4.) After a syrup has formed in the bottom of the bowl, stir well to be sure the sugar from the bottom of the bowl is incorporated, then pour this mixture into a heavy-bottomed non-reactive saucepan. (Don't use an aluminum, copper, or cast iron pan when cooking with citrus juice.)
5.) Bring to a boil over medium heat, stirring gently, and once boiling, cook for about 10 minutes or until the preserves are thickened to your liking.
6.) Ladle into clean jars, run a table knife around the edges to remove any air bubbles, and then wipe rims spotlessly clean.
7.) Wipe rims cleans with a damp paper towel.
8.) Place a sealing lid on top of jar then screw a band onto the jar until it's "fingertip-tight".
9.) Process for 10 minutes in a Boiling Water Bath.
10.) Turn kettle off and let jars rest in kettle for 5 more minutes.
11.) Remove jars from kettle using jar-lifter tongs, and gently set aside to cool on the counter, on a kitchen towel, in a draft-free place.
12.) Let rest for 24 hours, then check for proper seal before storing.
> If jars lid seals it will easily keep for one year in a cool, dark place. If jar doesn't seal, place it in your refrigerator and eat within 3 months, and within one month after opening.