- butter, for greasing
- 3 free-range eggs
- 115g/4oz caster sugar, plus 4 tbsp for dredging
- 1 unwaxed lemon, zest only
- 115g/4oz plain flour
- 200g/7oz icing sugar, sifted
- 125g/4½oz softened butter
- 2 tsp freshly squeezed lemon juice
- 125g/4½oz lemon curd
- Grease and line a 33cm x 23cm/13in x 9in Swiss roll tin with buttered baking parchment.
- Preheat the oven to 200C/400F/Gas 6.
- Put the eggs, 115g/4oz of the sugar and the lemon zest in a heatproof bowl and place over a pan of gently simmering water.
- Whisk with an electric whisk until the mixture is pale, creamy and thick enough to leave a trail when the whisk is lifted.
- Carefully remove the bowl from the heat and continue whisking for a further five minutes.
- Sift in half the flour and, using a large metal spoon, lightly fold it into the egg mixture.
- Sift in the remaining flour and fold into the mixture – it’s important to use gentle movements to retain as much air as possible in the batter.
- Pour the mixture slowly into the prepared tin and gently spread with a spatula so the base of the tin is evenly covered.
- Bake for 10–12 minutes until well-risen, pale golden-brown and firm to the touch.
- Place a damp tea towel on the work surface and cover with a sheet of baking parchment.
- Dredge with the four tablespoons of sugar – this will help stop the outside of the sponge sticking. Working quickly, turn the cake out onto the sugared paper and carefully remove the lining paper.
- Using a sharp knife, cut off the crusty edges from the two long sides. Roll the Swiss roll from one of the short ends, starting with a tight turn to make a good round shape and keeping the sugared paper inside the roll. Set on a wire rack and leave to cool.
- To make the icing, put the icing sugar and butter in a bowl and beat until smooth and creamy. Add the lemon juice and beat again.
- When the cake is cold, gently unroll but do not flatten it or it could crack.
- Spread the cake with then lemon butter icing, leaving a 1cm/½in border.
- Spoon the lemon curd evenly over the icing.
- Slowly roll the cake up again, enclosing the filling, and place on a plate. Sprinkle with extra sugar if you like.