This cake is a perfect example of the importance of using the highest quality ingredients you can find. Because just one orange flavors the entire cake, it’s important that the orange you use is fragrant with an oil-rich peel and a juicy interior. Organic, biodynamically-grown oranges are the best, and if you’re lucky enough to live someplace where local citrus is abundant, take advantage of it!
The walnuts in this cake add flavor and texture. To ensure they don’t get soggy, toast them first. Walnuts are more sensitive to burning than other types of nuts, so watch them closely in the oven. Once you start to smell them, they’re almost done. The best way to check walnuts for doneness is to taste one (carefully!) straight from the oven. Raw walnuts have a slightly bitter and acidic aftertaste. As soon as this bitterness disappears, they’re perfectly toasted.