For the rhubarb jam, peel the rhubarb, cut into finger-thick pieces and sauté lightly. Then puree.
Mix the jelling powder with dextrose and add, bring to the boil while stirring constantly and boil for 5 minutes until bubbly. If foam forms during boiling, skim it off before filling.
Fill prepared jars to the brim with rhubarb jam, seal immediately, invert and let stand on lid for about 5 minutes.