Preheat oven to 180C/ 350F /GM 4. Grease the base and sides of a 20 x 30cm Swiss roll tin and line the base with baking parchment. Do not line the sides
Put the eggs and yolk plus the sugar into the bowl of a stand mixer and whisk for around 5 minutes until pale & thick enough to leave a trail when a spoonful is lifted out of the bowl and drizzled back in (the ribbon stage)
Sift the flour and fold half into the batter using a metal spoon. Fold the remaining flour in, along with the lemon zest. Take care to fold in the flour very gently, so the air whipped in previously is not knocked out
Pour into the baking tin, spread out evenly and cook for 10-12 minutes until the sponge is golden and firm. Overbaking the sponge will increase the risk of the cake breaking up, so keep a close eye on the cake as it bakes
Meanwhile, lay a sheet of parchment onto a worktop and sprinkle with 1-2 tablespoon caster sugar
Working quickly, when the cake is baked remove it from the oven, run a sharp knife around the edges of the tin to loosen the cake and then immediately invert the tin over the parchment. The cake should come out of the tin easily
Remove the parchment used to line the tin from the back of the cake and trim the edges of the cake to neaten
Score a line across the short edge of the cake about 1.5 cm in (do not cut right through the cake though) - this will help the cake to roll
While the sponge is still warm (but not piping hot), roll the cake up into a tight spiral - use the parchment to help (the parchment will roll into the spiral of cake as you roll the cake). Let it cool completely on a wire rack