Portuguese airy sponge cake (Pão de Ló)

1. Preheat the oven to 180 °C; line a 24 cm round tin (ideally a ring tin) with baking paper that rises above the rim.

2. In a large bowl whisk the eggs, egg yolks, sugar and a pinch of salt with a mixer for at least 12-15 minutes until very thick, pale and tripled in volume.

3. Grate in the lemon zest.

4. Sift in the flour in three batches and fold in gently with a spatula from the bottom up so the foam doesn't collapse.

5. Pour into the tin and bake for 35-40 minutes until the top is golden and springy; don't open the oven during the first 25 minutes.

6. Leave to cool in the tin, then lift out with the paper and only peel the paper off when serving.

Tip: In the north of Portugal (Ovar) the centre of pão de ló is deliberately left creamy, almost runny – if you'd like it that way, bake it at 200 °C instead of 180 °C for 20-25 minutes and keep the middle wobbly.