Thoroughly wash and chop rhubarb into small pieces to release its juices.

In a large pot, combine chopped rhubarb, sugar, and water and stir to dissolve the sugar.

Bring the mixture to a gentle simmer over medium heat, stirring occasionally.

Simmer for 30 minutes until the rhubarb is softened and the liquid turns vibrant pink.

Remove the pot from heat and let the mixture cool slightly for 10 minutes.

Strain the mixture through a strainer or cheesecloth, pressing to extract all the juices.

Return the strained liquid to the pot and stir in vodka and vanilla extract if using.

Using a funnel, pour the liqueur into clean glass bottles, seal tightly, label with the date, and let infuse in a cool, dark place for at least one week before serving.