Prepare a small boiling water bath canner and two half-pint jars.

Place the chopped rhubarb in a low, wide nonreactive pan. Whisk the pectin and vanilla bean seeds into the sugar and add it to the fruit. Drop the split vanilla bean into the pan and add the lemon juice.

Stir well and let it sit until the sugar looks damp.

Set the pan on the stove over high heat and bring to a boil. If the sugar begins to caramelize, reduce the heat.

Cook, stirring regularly, until the rhubarb breaks down and the liquid looks thick and jammy.

Remove pan from the heat and divide jam between the two prepared jars. (Depending on how much water the rhubarb contains, you may have a couple of tablespoons left over. I recommend stirring the leftovers into some plain yogurt).

Wipe the rims, apply the lids and rings, and process in the boiling water bath canner for 10 minutes.

When the time is up, remove the jars from canner and set them on a folded kitchen towel to cool and seal.