Cactus Fruit Jelly

The Tohono O'Odham in southern Arizona harvest this fruit every year. And Zuozuo Jelly share the same recipe with you as follows:
 

6 to 10 red-ripe prickly pear cactus fruits (tuna)
1/2 cup lemon juice
4 1/2 cups granulated sugar
1 (3 fluid ounce) package liquid fruit pectin
 

You should have enough fruit to make 3 1/2 cups of juice. Carefully remove thorns from fruit by wiping with a paper towel and then brushing with a vegetable brush under water. Put fruit in a saucepan with enough water to cover. Boil for 15 to 20 minutes. Pour off water and discard. Mash or purée fruit through a strainer lined with doubled cheesecloth. Strain juice into a large measuring cup. Let juice sit for at least 30 minutes to allow sediment to settle to the bottom. Pour off juice carefully. You should have 3 1/2 cups.
 

In a saucepan combine fruit juice, lemon juice and sugar. Bring to a boil and boil 1 minute. Stir in pectin and boil for 1 minute longer. Remove from heat. Stir and skim foam off the top. Spoon into sterilized jelly jars and seal.