Preparation Steps

• Wash the grapefruits and lemons thoroughly. Cut off the ends of the grapefruits and lemons. Cut them in half crosswise.
• Scoop out the pulp from the grapefruits and lemons and place it in a large bowl. Reserve the peels.
• Scrape out the white pith from the peels and discard it. Slice the peels thinly.
• Add the sliced peels and the reserved pulp (including seeds, which help with setting) to a large, heavy-bottomed saucepan.
• Add the water and bring to a boil over medium-high heat. Reduce heat to low, cover, and simmer for 2 hours, or until the peels are tender.
• Remove the seeds from the pulp mixture by straining it through a cheesecloth-lined sieve into a separate bowl. Discard the seeds.
• Add the sugar to the saucepan with the tender peels and simmered liquid. Stir over medium heat until the sugar is completely dissolved.
• Increase the heat to high and bring the mixture to a rolling boil. Cook, stirring occasionally, for about 15-30 minutes, or until the marmalade reaches the setting point. To test, place a small amount on a chilled plate. If it wrinkles when pushed, it's ready.
• Remove from heat. Skim off any foam from the surface.
• Ladle the hot marmalade into sterilized jars, leaving about 0.5 inch of headspace. Seal tightly.
• Let the jars cool completely at room temperature, then store in the refrigerator.