Cut rhubarb into small segments, then add to a food processor. Pulse a few times until the rhubarb is small chopped.
In a sauce pan add rhubarb, sugar, and water. Bring to a boil, then simmer for 20 minutes on low.
Strain the juice and press the pulp against the stainer to extract every bit of juice.
Wash sauce pan, then add the strained juice. Bring to a boil and simmer on medium for 10 minutes longer until the liquid reduces and thickens a bit. Remove foam then pour in a sterilized bottle. Allow to sit for a couple of days before using. Keep refrigerated.
To serve, in a glass add ¼ cup rhubarb syrup and ¾ cup water. Mix well then add ice cubes. Enjoy!
Recipe by My Persian Kitchen at http://www.mypersiankitchen.com/sharbat-eh-rivas-rhubarb-syrup/