Preheat oven to 220°C (200°C fan-forced). Place a 25cm cast iron skillet in the oven to heat up at the same time.
When the oven is ready, take the skillet out of the oven, melt butter in the pan, swirling around so it coats the sides. Stir in brown sugar and cinnamon. Add apple, stir to coat, flatten to one layer and place back in the oven for 5 minutes, stirring again half way.
Meanwhile, in a blender, mix together eggs, vanilla extract, caster sugar, salt, flour, and milk. Pour egg mixture into skillet over the apples, swirl a little and bake until puffed and brown, around 15 - 20 minutes.
Remove from oven, top with half the berries, and a sprinkle of icing sugar. Serve with remaining berries and lemon wedges or maple syrup.
If you don't have a cast iron skillet, you can use an oven proof frying pan, or non springform cake tin.