Score each pomegranate around the equator and break it open in a deep bowl of water. The arils sink while the bitter white membranes float, making them easy to separate. Discard the membranes and pith.

Drain the arils and place them in a heavy-bottomed saucepan with 1/2 cup of water. Bring to a low simmer, then mash with a potato masher to release the juice. Cook for 5 to 10 minutes, until the arils have given up most of their color and the liquid is bright pink-red.

Transfer the cooked mixture to a dampened jelly bag or strainer lined with several layers of cheesecloth set over a deep bowl. Let it drip undisturbed for at least 2 hours. Don't squeeze the bag; squeezing releases membrane bits that cloud the finished jelly and add bitter flavor.

Measure 3 1/2 cups of strained juice for the next stage.

Prepare half-pint canning jars by washing in hot soapy water, rinsing, and keeping warm. Have lids and rings ready.

Combine the pomegranate juice and lemon juice in a heavy-bottomed jam pot. Whisk in the powdered pectin until fully dissolved.

Bring to a hard rolling boil over high heat, stirring frequently. Add the sugar all at once and stir constantly until fully dissolved. Return to a hard rolling boil that can't be stirred down, and boil hard for exactly 1 minute.

Remove from heat and quickly skim off any foam.

Ladle the hot jelly into prepared half-pint jars, leaving 1/4 inch headspace. Wipe rims clean and apply two-piece canning lids fingertip tight.

Process the filled jars in a boiling water bath canner for 10 minutes (adjust for altitude — see notes).

When the timer goes off, turn off the heat and let the jars sit in the canner for another 5 minutes before lifting them out. This helps prevent siphoning.

Cool on a towel for 12 to 24 hours, check seals, and refrigerate any unsealed jars. Sealed jars keep on the pantry shelf for 12 to 18 months.