In a heavy saucepan over medium heat combine sugar and water. Stir to dissolve sugar. Add rhubarb and allow to simmer for 15 minutes or until tender. Add strawberries and lemon juice and simmer for 10 minutes more. Allow mixture to cool for about 10 minutes.
In batches, if necessary, puree mixture in blender. Add water if mixture appears too thick. Drizzle over yogurt or ice cream or serve with crumpets and sweetened whipped cream.