This recipe is adapted from Claudia Roden. This cake has north African and Spanish roots. According to Claudia, citrus cultivation and trade was particularly associated with Sephardi Jews around the Mediterranean, and there are any number of orange cake recipes in Sephardi culture.
Don't worry if the cake sinks as it cools, or in fact turns out looking rather boring. Trust me it is delicious, especially if served as a pudding with freshly sliced blood oranges and whipped cream.