Pink Grapefruit Marmalade

A FAQ I am asked is "Can I use less sugar?" In jams and marmalade, sugar doesn't just sweeten; it preserves and gels. I tried this with less sugar and it began reducing too much before it jelled, which would have resulted in a thick, dry marmalade. So the best strategy with this, or any jam or marmalade, is to make the recipe as written, and eat less of it. Adding a swipe of ricotta or labne to toast before adding marmalade, is a good way to use less while still enjoying some of the confiture. To test the jam for doneness, you can either insert a candy thermometer into the pot in step 4, or you can put a plate in the freezer and use a variation of the "wrinkle test," turning off the marmalade when you think it's done (to avoid overcooking) and putting a spoonful on the chilled plate. Return the plate to the freezer 3-5 minutes then nudge the marmalade with your finger; if the syrup is thick and holds its shape, it's done. Unlike other preserves, I leave this one a little looser and it doesn't need to quite wrinkle. I don't can jams and usually just store them in the refrigerator, but if you'd like information on how to do that, check the National Center for Home Food Preservation website.

Servings cups (2,2kg)

4 medium pink grapefruits, (about 2 1/2 pounds, 1kg), preferably unsprayed or organic
5 cups (1,4l) water, plus more for cooking the grapefruit slices in step 3
3 1/2 cups (700g) sugar
the juice of 1 lemon

Cut the grapefruits in half. Use a soup spoon to scrape the pulp out of four of the grapefruit halves*. Remove any seeds and coarsely dice the grapefruit pulp and scrape it, along with any juice on the cutting board, into a bowl. (If you have one of those cutting boards with a gutter to collect meat juice, those work well here, as well as in the next step.) Set aside.
Cut the remaining four grapefruit halves in half, remove the seeds, and use a sharp knife (I like to use a serrated bread knife) to cut the grapefruit in slices as thin as you'd like. I try to get them as thin as a coin, but sometimes I get impatient so don't always reach that goal. Take care using the knife as the fruit pieces can be slippery.
Put the grapefruit slices in a large non-reactive pot or Dutch oven. (Any juices on the cutting board can be scraped into the bowl of grapefruit pulp.) Cover the grapefruit slices with water, add a pinch of salt, cover the pot, and bring to a boil.
Reduce the heat to a simmer and cook for 5 minutes. Turn off the heat and let the grapefruit slices sit in the hot water until they're soft and translucent. Strain the grapefruit slices, discarding the water, and place the cooked grapefruit slices back in the pot or Dutch oven along with the chopped grapefruit pulp, 5 cups of water, sugar, and lemon juice.
Cook the mixture over medium-high heat until it reduces and the marmalade has thickened and become syrupy. If using a candy thermometer, it'll read around 216-218ºF (102-103ºC.) Otherwise, check the headnote before the recipe for how I test this particular marmalade for doneness.
Ladle the hot marmalade into clean jars and cover.

Notes

*You can use the grapefruit rinds to make Candied Grapefruit Peel.