Greaseproof a cake tin and preheat the oven to 180°C/350F.
Carefully, cut slits halfway through each apple quarter, leaving ¼ inch uncut nearest the core section.
You want the quarters to remain whole, so carefully slice without cutting all the way through.
Place the sliced quarters in a bowl with the lemon juice and sugar, stirring to coat and set aside.
Place the butter and sugar into a bowl and beat with an electric mixer until light and fluffy, approximately 1 ½ minutes if using a hand beater.
Add the vanilla extract and egg yolks and beat until well combined, approximately 1 minute if using a hand beater.
In a separate bowl, place the flour and baking powder and stir to combine.
Add the dry mixture in thirds to the butter mixture until just combined and no dry portions remain in your bowl.
Place the egg whites into a separate bowl and beat until stiff.
Spoon a third of the cake batter into the stiff egg whites and fold through until combined and no lumps remain.
Repeat with the remaining cake batter in a further third and fold through until the mixture is fully combined.
Pour the cake batter into the prepared tin and spread out evenly.
Press the apple quarters into the cake in your chosen pattern and place in the oven to bake until a skewer comes out clean and it is golden on top, approximately 50 minutes.
Remove and allow to cool.
Slice and serve as is or with a little cream.