Preheat the oven to 170 degrees Celsius. Prepare a 2 lb loaf tin by lining it with baking parchment or a tin liner.
Peel and core the apples. Cut them into small pieces.
In a large bowl, beat together the butter and sugar until well combined.
Crack one egg into the bowl. Beat until mixed, then repeat with the other two eggs.
Fold in the flour and cinnamon, making sure that there are no pockets of flour anywhere.
Add the apple and mix one final time. Spoon the mixture into your loaf tin and put in the oven for 1 hour or until risen, golden and cooked through. Allow to cool slightly in the tin.
Notes
Cake can be frozen after baking. Once cooled, wrap well and transfer to the freezer. Freeze for up to 3 months. Defrost thoroughly before eating.