Step 1

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.

Step 2

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.

Step 3

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.

Step 4

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.

Step 5

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.

Step 6

Ladle the hot marmalade into clean jars and cover.