Rinse twist-off jars and lid with hot water. This way bacteria that could spoil the jam have no chance. Then drain glasses upside down on a clean tea towel.
Wash the strawberries, cut off the green stalk. Halve or quarter the strawberries depending on their size.
Cut the ends and leaves off the rhubarb. Wash the sticks. Grasp the hard fibres at one end of the stick with a kitchen knife and pull them off lengthwise. Cut the rhubarb into pieces about 2 cm in size.
Cut the vanilla pod in half lengthwise. Scrape out the vanilla pulp with the blunt back of the kitchen knife.
Put a total of 1 kg of strawberry and rhubarb pieces in a large pot. Mix with vanilla pod, vanilla pulp, lemon juice and jam sugar.
On your mark, get set, go! Bring everything to a boil over high heat, stirring continuously. Only when the strawberry-rhubarb mix is boiling, the official cooking time begins. Simmer the fruits for 3-4 minutes until they are bubbling.
Stir continuously so that nothing burns.
If foam should form on the surface, please skim off with a skimmer. Why? Foam is a breeding ground for bacteria and also brings air bubbles into the jam. Not cool!.
It will be exciting! Gelling test 1.0 - for this, take off some jam with a wooden spoon and put it on a cold saucer. Wait a short time! Now push the jam together with the wooden spoon. If jelly-like wrinkles form, the jam is ready to be filled.
If not, boil them for another 1-2 minutes.
Immediately pour the jam into a measuring jug or use a funnel to fill the jars brimful by brim. Screw the jars tightly and turn them upside down for about 5 minutes. This allows the remaining air to escape.
Then turn again properly, screw tight again and let the jam cool down completely. This is what summer tastes like, friends!