Preheat the oven on to 160C (320F). Line a 23cm (9inch) round spring-form cake tin with baking paper.
In a medium-sized heatproof bowl, melt the butter and dark chocolate at a low heat. Microwave for 30 seconds at a time, then stir. Repeat until fully melted. Add the brown sugar, cocoa powder, egg yolks and whisk well.
In a clean bowl, whisk egg whites at a medium speed until soft peaks form. Add the caster sugar and continue beating until glossy and smooth.
Transfer the chocolate mixture into a large bowl. Fold a third of the egg whites into chocolate mixture. Then gently fold in the almond meal. Fold the remaining egg whites in until the mixture just comes together. Fold in the raspberry.
Bake for 50-60 mins or until a skewer comes out with crumbs and is not wet. Let it cool in the tin. Dust with icing sugar before serving. Store the cake in an airtight container in at room temperature for 2 days for in the fridge for 5 days.
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.