Preheat the oven to 160C(320F) fan-forced. Grease and line the base of a round spring-form tin.

Melt the chocolate and butter together in the microwave (or on the stove) and set aside to cool.

Beat together the eggs and sugar until about tripled in volume, pale and moussy. This is easiest in a freestanding mixer but you can use a hand held if you need. Be prepared for a little arm workout though.

Mix the almond meal with the cocoa powder and fold this gently into the egg and sugar mixture, followed by the chocolate and butter then fold in the zest and juice of the lime.

Pour and scrape the mixture into the prepared tin and bake in the preheated oven for 40-45 minutes. Nigella says that the cake will be just firm on top but still have a bit of wobble.

Remove from the oven and sit the cake in the tin on a wire rack to cool. Once the first heat has left it, drape a clean tea towel over the cake to stop it getting too crusty (unless you like it like that which I do).

When cold, remove the cake from the tin and dust with icing sugar.