Combine chopped rhubarb and strawberries into a small pot. Heat over low-medium heat until it cooks down a bit (about 10-15 min), stirring/ “smashing” occasionally.
It should form a jam-like substance. Add in the chia seeds, vanilla, lemon juice/zest and salt. Stir and let cook over low heat for another few minutes or so. Turn heat off and let cool before adding to jar.
It will thicken as it cools and also once refrigerated! Keeps for up to 3 weeks.