Lightly grease a 20cm round cake tin. Line the base and sides of pan with double-thickness baking paper to extend 2cm above the side of pan.

Sift icing-sugar mixture and flour through fine sieve into bowl. Stir in almond meal and lemon zest until well combined.

In another bowl, lightly whisk egg whites for a few seconds until broken down. Add egg whites, melted butter, milk and 100g of frozen blueberries to the almond mixture. Stir until just combined.

Spread cake mixture into prepared cake tin. Scatter over remaining blueberries, gently pressing them into the mixture slightly.

Bake at 180°C for about 1 hour and 10 minutes, or until cooked when tested with
a skewer. (Be careful not to overcook the cake or it will be too dry.)

Turn cake out onto a wire rack to cool.