This dessert manages to be both rich and light, with just the right balance of sweetness and acidity. The batter is made from milk, citrus, butter, sugar and whipped egg whites for a fluffy texture, and it requires just one preparation. As it bakes in a hot water bath, the batter separates into a soft cake on top and a silky and citrusy cream at the bottom. It's a treat that stays refreshing even when served warm.