Add the rhubarb, sugar, and water to a small saucepan. Stir well to help the sugar dissolve.
Bring to a simmer. Cover. Reduce heat to medium-low and simmer for 20 minutes, or until the rhubarb is very soft and the liquid is vibrant red and reduced by about 1/3.
Remove the pot from the heat and let cool. Strain through a fine-mesh strainer to seperate the solids from the syrup.