Cut the rhubarb into small pieces, clean the strawberries. Squeeze the lime.
Put the rhubarb, strawberries and lime juice in a pot. Simmer the mixture until the rhubarb is soft.
Puree the mixture with a hand blender. Stir in the vanilla and preserving sugar and bring to a boil briefly.
Refrigerate the jam overnight. The next day, boil again and fill into jars while still hot.