During years where we get a good amount of rain (good means we're no longer measuring annual rainfall in single digits), the cactus fruit is plump and juicy, and this year's harvest was a good one.
Wash/sterilize and then heat 5 half-pint jars in a warm oven. Heat 5 lids in water that is barely simmering.
Mix the following:
2 1/2 cups prickly pear juice
3 Tbsp lemon juice
1 package pectin
1 tsp butter
Bring to a boil.
Stir in 3 1/2 cups sugar. Bring to a full rolling boil, and boil for three minutes. Ladle into hot jars. Wipe rims of jars with a clean damp cloth.
Place hot lids on jars, centering to ensure a good seal. Screw lid bands on. Turn jars upside-down onto a towel for five minutes to "process" (no need to mess with a boiling water bath). Turn right side up and allow to cool and seal (you'll hear the lid pop when the seal is successful). The jelly will keep in a cool pantry for at least a year.