2 1/2 c. rhubarb, cut in 1/2-in. pieces
1/3 c. plus 1/2 c. sugar, divided
1/3 c. cranberry juice
4 egg yolks
2 tbsp. unsalted butter, cut into 4 pieces
Prep Day: In a saucepan over medium heat, combine rhubarb, 1/3 cup sugar and cranberry juice and cook, stirring frequently, until rhubarb breaks down into a sauce, about 10 minutes. Remove from heat and set aside.
In a saucepan (large enough over which a medium bowl might fit) over medium-high heat, bring about 2 inches of water to a boil. While water is heating, whisk egg yolks, remaining ½ cup sugar and salt in a medium bowl. Reduce heat to keep water at a simmer and place bowl over saucepan, whisking constantly until yolk mixture begins to thicken. When yolks are quite warm, whisk in rhubarb mixture, stirring constantly until mixture thickens. Add butter, 1 piece at a time, whisking well, then remove bowl from heat and set aside to cool. Refrigerate in a tightly covered container for up to 1 week.
To Serve: It’s great on warm scones or toast or dolloped alongside a slice of angel food cake or on a bowlful of fresh strawberries.