In a large saucepan, combine rhubarb, strawberries, sugar, and lemon juice.

Bring to a boil over medium-high heat, stirring frequently.

Reduce heat and simmer for 10–15 minutes until fruit is soft.

Stir in the pectin and return to a full rolling boil for 1 minute.

Remove from heat and skim off any foam.

Pour into sterilized jars, leaving 1/4-inch headspace.

Wipe rims, seal with lids, and process in a boiling water bath for 10 minutes.

Let cool and check seals before storing.