* To ensure cake is gluten-free/wheat-free, dust the pan with unsweetened cocoa powder instead of flour.
* Don't like chocolate and orange together? You can leave out the orange zest and substitute your favorite liqueur (or just leave it out). Do not use a tablespoon of extract as that's too much (you could use a teaspoon).
* Recipe can be doubled.
* Cake freezes well – wrap tightly and freeze for up to three months.