Cut the strawberries into small pieces, mix well with the squeezed lemon juice and the scraped-out vanilla pod (only use the pod, not the contents!), The sparkling wine and the preserving sugar and leave to stand for approx. 12 hours or overnight.
Peel the rhubarb, cut into 1 - 2 cm pieces and bring to the boil with the water. Cook for about 30 minutes from the boiling point. Caution: it boils over easily! Then drain the rhubarb well in a fine sieve. (I like to use the collected brew for further processing into rhubarb syrup). Finally, squeeze out again firmly with a spoon so that all the liquid goes out. Set aside the fruit puree (should make approx. 300 g).
Now bring the strawberry, sparkling wine and sugar mixture to the boil while stirring. Let simmer for 4-6 minutes from the boiling point. Take out the vanilla pod.
When the strawberries are soft enough, press medium fine with a potato masher. Now add the rhubarb puree. Stir well and bring to the boil again. Pour the jam hot into prepared (hot) twist-off jars, screw on tightly immediately and allow to cool.
Tastes good on fresh rolls, on pancakes, in natural yoghurt or quark.