Rhubarb Simple Syrup

Combine rhubarb, sugar and water in a medium saucepan. Split vanilla bean, scrape out the sticky black seeds with the tip of a small, sharp knife and add them and the pod to the pan. Bring to a boil. Reduce heat to a simmer and cook, stirring occasionally, until the rhubarb is very soft, 15 to 25 minutes. Strain the mixture through a fine-mesh sieve into a bowl, pressing on the rhubarb to extract all the syrup.