Ingredients :

• Almond flour — This is the central ingredient, not the flour. Get it as fresh as possible — almond flour that starts to smell rancid will ruin the whole cake. If you have some lying in the cupboard for six months, buy a new one; it’s really worth it.
• The orange — Untreated, really. Not for ideological reasons, but because you’re going to zest the skin and if it’s covered in treatments, you’ll taste it in the batter. A beautiful Valencia orange or a thick, juicy Navel — avoid small, thin-skinned oranges that yield almost nothing when zesting.
• Melted unsalted butter — Melted, not hot. The difference is important: if you pour boiling butter over your beaten eggs, you’ll start cooking them. Melt it gently, then let it cool down while you deal with the rest.
• Baking powder — One whole sachet, no more, no less. This is what will slightly aerate the already dense almond batter. Without it, you get a compact fondant — not bad, but different from what we are looking for here.