In a large pot combine the water, rhubarb and lemon zest. Allow it to come to a boil. Once boiling, reduce the heat and continue to simmer for approximately 15 minutes. At this point, add the strawberries and cook for another 2 to 3 minutes.
Remove the pot from the heat and allow it to cool completely. Once the mixture is at room temperature, use a hand blender to purée it all. When a smooth texture takes form, stir in the lemon juice. You may find you do not need all the lemon juice, so add it in portions until you feel it’s enough from the taste of it.
Place the lemonade in the refrigerator until very cold before serving.