Vanilla and blueberry angel cake

10 egg whites

1 tsp cream of tartar

pinch of fine sea salt

1 tbsp lemon juice

1 vanilla pod, sliced lengthwise and the sticky interior scraped out

300g caster sugar

125g plain flour

100g blueberries

For the icing:

150g icing sugar

1 tbs orange juice

1 tbs blueberry compote