Preheat the oven to 180C/160C Fan/Gas 4.
Rub the butter into the flour until it resembles fine breadcrumbs.
Stir in the sugar and cinnamon.
Peel, core, and dice two and a half apples.
Stir the diced apples into the cake mixture with the eggs.
Divide the mixture into two loaf tins.
Thinly slice the remaining half of the apple and arrange on top of each cake.
Sprinkle with demerara sugar and bake for 35-45 minutes.
Brush the top of the cakes with the apricot jam.
Allow to cool in the tins for 10 minutes before turning out.