Prepare Your Tin and Oven: Preheat your oven to 160°C (140°C fan/Gas Mark 3). Grease a 20cm round baking tin generously and line the base with baking parchment. Place the tin inside a larger roasting tray; this will be used for a water bath, ensuring an even, gentle bake.

Cream Butter and Sugar: In a large mixing bowl, using a stand mixer or hand mixer, cream together the softened butter and caster sugar until the mixture is light and fluffy, taking on a pale, creamy yellow hue. Scrape down the sides of the bowl to ensure everything is well combined.

Incorporate Egg Yolks and Flavourings: Add the egg yolks one at a time, beating well after each addition until fully incorporated and the mixture looks smooth and glossy. Stir in the alcohol-free vanilla extract, lemon zest, and fresh lemon juice. The aroma of lemon will start to fill your kitchen at this stage.

Add Flour and Milk: Gradually beat in the plain flour until just combined, being careful not to overmix. The batter will be thick. Slowly pour in the warm milk, mixing constantly until the batter is smooth and quite thin, like a pouring custard.

Fold in Egg Whites: In a separate, clean bowl, whisk the egg whites until they form stiff peaks. They should be glossy white and hold their shape firmly. Gently fold the stiff egg whites into the batter in three additions. Do this carefully, trying to retain as much air as possible. The mixture will look quite liquid with fluffy white clouds floating on top – this is exactly what you want.

Bake the Cake: Pour the ethereal batter into your prepared baking tin. Carefully pour hot water into the larger roasting tray, around the baking tin, so it comes about 2-3cm up the sides of the tin. This water bath is essential for the custard layer to set beautifully. Bake for 60-70 minutes. When ready, the top should be a light golden-brown and feel springy to the touch. A slight wobble in the centre is normal, indicating the custard layer is still delicate.

Cool and Chill: Remove the tin from the water bath and let it cool completely on a wire rack. Once at room temperature, cover the cake and chill it in the refrigerator for at least 4 hours, or ideally overnight. This chilling time is crucial for the layers to fully set and firm up.

Serve: Once thoroughly chilled, carefully remove the cake from the tin. Dust generously with icing sugar before slicing and serving. Each slice will reveal the distinct magic of its three layers, a true feast for the eyes and the palate.