Firstly make the compote. Place all the ingredients together in a saucepan over a low heat and cook for about 10-12 minutes or until the apple is cooked (some of it will turn in to a saucy pulp and some of it will retain its shape better - this is what you want). Check the sweetness or acidity and correct to your taste with sugar or lemon juice.
Once you’re happy with it, spoon everything into an oven proof dish, large enough to top with the sponge.
Whilst the apple is cooking you can make a start on the sponge.
First beat the butter, sugar and vanilla until pale and fluffy. Add the egg a little at a time until all is combined; if the mixture starts to separate just add 1 or 2 spoonfuls of flour to stabilise and continue adding the eggs until fully incorporated.
Next add the flour and bring together.
Spoon or pipe onto the apple compote, sprinkle with the almonds or Demerara sugar if using and bake for around 20 minutes at 180C/350F/GM4 until cooked and a skewer inserted into the sponge comes out clean.
Our thanks to the National Trust for providing this recipe.