Start by sterilizing your jars, lids, and rings in boiling water for about 10 minutes.

Gather all fresh ingredients and prepare them: chop rhubarb, hull and halve strawberries, measure sugar and lemon juice.

In a pot, combine rhubarb, strawberries, sugar, lemon juice, vanilla extract, and salt. Let sit for 10 minutes.

Cook the mixture over medium heat, bringing it to a boil and stirring occasionally.

Once boiling, reduce heat to maintain a gentle boil, cooking for 45 to 60 minutes.

Use a thermometer to check if the jam reaches 220°F or check for a wrinkle on a cold plate.

Ladle the hot jam into sterilized jars, leaving about 1/4 inch of headspace.

Wipe the rims of the jars clean, secure lids, and process in a boiling water bath for 10 minutes.

Remove jars and let cool for 24 hours without disturbing.