Preparation

1. Put the chopped rhubarb and sugar into your pot. Stir, then let it sit for 20 to 30 minutes to pull out juices.
2. Set the pot over medium heat and stir until the sugar dissolves and everything turns juicy. Add the lemon juice.
3. Bring it to a gentle boil and lower the heat to keep it bubbling without splattering. Stir often.
4. After about 15 to 25 minutes, the rhubarb should look broken down and glossy. Stir in the cinnamon.
5. To check thickness, spoon a little jam onto a cold plate and wait 30 seconds. If it wrinkles, it’s ready. If watery, cook a few more minutes.
6. If using vanilla, stir it in right before filling jars.

Canning Process

1. Wash jars, lids, and bands. Keep jars warm.
2. Fill the canner with enough water to cover jars by 1 to 2 inches and bring it to a simmer.
3. Ladle hot jam into jars, leaving 1/4 inch headspace. Wipe rims, add lids, and screw bands on fingertip tight.
4. Lower jars into simmering water, bring to a full boil, and process for 10 minutes (follow safe canning times for your altitude).
5. Remove jars and let them sit untouched for 12 to 24 hours to seal.