Preheat the oven to 180°C (350°F).

Peel, core, and slice the cooking and eating apples into thin wedges. Cook them in a medium saucepan with a splash of water for about 5-7 minutes until softened.

In a large mixing bowl, cream together butter and caster sugar until light and fluffy, about 2-3 minutes.

Add the grated lemon rind and gradually sift in the plain flour while folding it to create a smooth batter.

Slowly whisk in the warm milk until smooth, ensuring no lumps remain.

Incorporate the egg yolks and vanilla bean paste until fully mixed.

Layer the softened apple slices in a prepared baking dish and pour the custard mixture over them.

Mix together demerara sugar and ground cinnamon, then sprinkle evenly on top of the custard.

Bake for approximately 20 minutes until the top is golden brown and slightly puffed.

Let cool for a few minutes before serving warm, optionally with vanilla ice cream or whipped cream.