01 -
Preheat your oven to 200ºC/400ºF/gas 6.
02 -
Put the butter and sugar in a mixing bowl, grate in the lemon zest, and cream together until pale and fluffy.
03 -
Separate the eggs, then gradually add the egg yolks and flour, beating after each addition to avoid lumps.
04 -
Add the milk and 3 tablespoons of freshly squeezed lemon juice, and mix well.
05 -
In a separate clean, dry bowl, whisk the egg whites until stiff peaks form. Gently fold them into the rest of the mixture, taking care not to deflate the egg whites.
06 -
Pour the mixture into a buttered ovenproof dish (about 1.5 liters or 1.5 quarts). Stand the dish in a roasting tin filled with water about one-third up the sides of the dish.
07 -
Bake in your preheated oven for about 45 minutes, until the top is set and spongy and it has a nice golden color.