GRAPEFRUIT-AND-MEYER-LEMON MARMALADE

Steps:

• Remove the grapefruit skin with a vegetable peeler. Cut the peel into 1/8-inch slivers; stop when you have 3/4 cup. Discard the rest. Slice off the ends of the grapefruit and the remaining grapefruit peel and pith. Remove grapefruit segments, reserving membrane. Stop when you have 5 cups of segments.
• Cut the ends off the Meyer lemons, deep enough so you can see the flesh. Leaving the peel on, remove the segments of lemon and reserve the membrane. Cut the segments crosswise into 1/4-inch pieces. Put membranes from the grapefruit and Meyer lemons in a jelly bag and tie closed.
• In a wide and deep pot, combine the grapefruit segments, grapefruit peel, lemon pieces and jelly bag. Add lemon juice and 2 1/2 cups water. Simmer until the grapefruit peel is tender, 25 to 30 minutes. Let cool.
• Preheat the oven to 225 degrees. Working over a bowl in your sink, squeeze the liquid from the jelly bag; keep squeezing and wringing it out until you extract 1/3 to 1/2 cup of pectin. Add pectin and sugar to the pot. Place over high heat and boil, stirring now and then, until marmalade is between 222 and 225 degrees and passes the plate test. (Spoon a little onto a plate and put in the fridge for 3 minutes. If it thickens like jam, it is done.)
• Meanwhile, put 6 sterilized 8-ounce canning jars and lids on a baking sheet and place in the oven. When jam is done, remove jars from the oven. Ladle jam into the jars, filling them as high as possible. Wipe the rims. Fasten the lid tightly. Let cool. If you don't get a vacuum seal, refrigerate the jam.