How to Prepare
1. In a large heavy bottomed pot, combine rhubarb, strawberry, and water together over high heat. Bring to a boil, reduce heat and simmer for 10 minutes. Skim any scum that might come to the surface with a ladle.
2. Pour rhubarb juice into cheesecloth or jelly bag and let drip overnight in the refrigerator. Do not squeeze the bag.
3. Measure 4 cups (1 L) of rhubarb liquid and pour into a large heavy-bottomed pot. Scrape vanilla seeds out of the pods using a paring knife and add them to the liquid.
4. Add the pectin and stir the liquid with a wooden spoon until the pectin is dissolved and the vanilla seeds are distributed.
5. Place the pot over high heat and bring to a boil, stirring constantly. Add sugar in a steady stream, stirring all the while. Return to a full boil while continuing to stir the jelly.
6. Boil hard for 1 minute. Remove from heat and use a plastic ladle or wooden spoon to skim off any foam on the top. Discard vanilla bean husk.
7. Ladle jelly into jars within ¼ inch (6 mm) of rim. Wipe the rims with a warm cloth. Add the lids and the rings, tighten just until finger-tip tight.