01 -
Combine lemon juice, rhubarb, strawberries, and sugar in a saucepan over medium heat.
02 -
Stir occasionally while cooking on medium-low for around 1 hour. Once thick and over 220°F, it's ready.
03 -
Boil 1-cup jars, their lids, and rings for ten minutes or clean them in the dishwasher to sterilize.
04 -
Spoon hot jam into the prepared jars, leaving a little space (1/4 inch) at the top. Close the jars with rings and tighten slightly.
05 -
Put the closed jars in a big pot of boiling water (1 inch above jars) for 10 minutes.
06 -
Leave jars untouched on a towel for a full day (24 hours) until the lids seal properly.