Prepare the apples – Place the sliced apples into a saucepan with 50 g of the sugar and 2 tablespoons of water. Cook gently over medium heat for 5–7 minutes until the apples soften but still hold their shape.

Preheat the oven – Set the oven to 180°C (160°C fan) and lightly grease a shallow baking dish.

Layer the apples – Spoon the warm apples evenly into the prepared dish, spreading them out so the base is level.

Cream butter and sugar – In a mixing bowl, beat the softened butter with the remaining 100 g sugar until pale and fluffy. This step helps create a light sponge.

Add the eggs – Beat in the eggs one at a time, mixing well after each addition to keep the batter smooth.

Fold in dry ingredients – Gently fold in the self-raising flour, followed by the milk, vanilla extract, and lemon zest if using. The batter should be soft and spoonable.

Top the apples – Spoon the sponge mixture over the apples, spreading carefully to cover them without pressing down.

Bake the pudding – Place the dish on the middle shelf of the oven and bake for 30–35 minutes until the sponge is risen, golden, and springs back when lightly pressed.

Rest before serving – Allow the pudding to stand for 5 minutes so the layers settle and slice cleanly.