4 large (1 pound) rhubarb stalks, chopped
1 cup granulated sugar
1 cup brown sugar2 cups water4 tablespoons freshly squeezed lime juice, or to taste
Combine the rhubarb and sugar in a medium, thick-bottomed saucepan. Stir well, and leave for 45 minutes or so (unheated), stirring now and then.
Add the water and bring to a gentle simmer over medium heat, stirring until the sugar dissolves. Continue to simmer for another 15-20 minutes, until the rhubarb starts to break down. Carefully strain into a bowl through a fine strainer. Transfer back to the saucepan, stir in the lime juice, and bring to a simmer. Let simmer over medium heat for another 15 minutes or until the syrup has reduced quite a bit and thickened. Remove from heat and allow to cool completely.