Place juices, water, and sugar in a steam kettle. Bring to boiling, making sure sugar is fully dissolved. Temper in yolks. Continue cooking, whisking continuously until mixture thickens and reaches nappe (180°F). Place in mixer and cool slightly. Start incorporating the butter. Pour in molds or tart shells while still warm.
Chef's Note Blood Orange Curd also can be used as a sauce or topping.