Preheat the oven to 180°C. Grease two 19 x 8cm loaf tins with non-stick spray and line with baking paper.
1. Beat the egg yolks and 200ml of the sugar until thick and pale yellow. Beat in the yoghurt and lemon zest. Using a large metal spoon, fold in the polenta or mealie meal and ground almonds.
2. Whisk the egg whites until stiff peaks form. Add the remaining sugar in two parts, whisking after each addition until the sugar has dissolved. Fold into the polenta mixture.