Place the rhubarb, strawberries, and maple syrup in a medium saucepan over medium heat. Stir frequently once it starts to simmer. Cook for 5-10 minutes until the fruit is softened.
Add the chia seeds to the mixture, and continue cooking over low heat until thickened to your desire. It does continue to thicken once removed from heat. I like to cook for no more than 10 minutes. Remove from heat.
Add the lemon juice and vanilla.
Place in a jar or glass container. Store in fridge once cooled. Will keep up to two weeks in refrigerator.