Strawberry-Rhubarb Jam

1 . Stage

Place rhubarb, strawberries, lemon juice, pectin, and butter into a large kettle over medium heat. Stir and bring to a boil. Add sugar, 1 cup at a time, stirring constantly until sugar is dissolved and juice begins to form. Increase heat to medium-high, bring mixture to a rolling boil, and cook and stir for 1 minute. Skim off any foam that forms.

2 . Stage

Sterilize the jars and lids in boiling water for at least 5 minutes. Use a jelly funnel and soup ladle to pack jam into hot, sterilized jars, filling to within 1/4 inch of the top. Run a knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe the rims with a moist paper towel to remove any food residue. Top with lids and screw rings on tightly.

3 . Stage

Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil over high heat, then carefully lower the jars into the pot using a holder. Leave a 2-inch space between the jars. Pour in more boiling water to cover jars by at least 1 inch. Bring to a rolling boil, cover, and process for 5 minutes.

4 . Stage

Remove the jars from the stockpot and let rest, several inches apart, for 12 to 24 hours. Press the center of each lid with a finger to ensure the lid does not move up or down. Remove the rings for storage and store in a cool, dark area.