Rinse the rhubarb, remove the ends, and peel. Cut the rhubarb into 1-2 cm (approximately 1/2-3/4 inch) wide pieces. Remove the zest in strips from the lemon, then squeeze the juice. Halve the vanilla bean lengthwise and scrape out the seeds. Mix the lemon juice, lemon zest, cinnamon, vanilla seeds, and the rhubarb in a saucepan. Bring the mixture to a boil, then reduce the heat and simmer for 5 minutes. Remove the spices and the lemon zest from the pan.
Add the jam sugar and bring to a boil, stirring constantly. Cook the mixture for 4 minutes.
Fill the prepared screw-top jars to the brim with the hot jam. Seal tightly, and cool completely.