Lemon and pistachio Battenberg

FOR THE LEMON SPONGE:
1 Preheat the oven to 180 degrees (160 fan). Grease and line a 20cm x 20cm square baking tin with parchment paper. Cut a large piece of tinfoil and fold it a few times to make a thick divide for the sponges. Place this in the centre of the tin and set the tin aside.

2 Cream the butter and sugar together until pale and soft, then add the egg. Beat well, then add the lemon zest, juice, flour and yellow food colouring. Fold together until just combined, then spread into one side of the prepared tin.

FOR THE PISTACHIO SPONGE:
1 Use the same bowl as for the lemon sponge to cream the butter and sugar together. Add the egg, followed by the milk, flour, ground pistachios and green food colouring, folding together until just combined. Spread into the other side of the tin and bake for 30-35 minutes until a skewer inserted into the centre comes out clean. Leave to cool in the tin.

FOR THE MARZIPAN:
1 Mix the ground almonds, caster sugar and icing sugar together in a bowl. In a separate bowl, whisk the lemon juice, egg and almond extract together, then slowly add to the dry ingredients.

2 Bring the marzipan together with your hands, then knead for a minute or two until you have a soft pliable dough. Chill for 30 minutes.

TO ASSEMBLE:
1 Place the sponges on top of each other and trim the edges so that they are even and the same size, then cut each coloured sponge in half lengthways.

2 Dust the work surface with icing sugar, then roll out the marzipan to a large rectangle, about 40cm x 20cm.

3 Spread about two tablespoons of lemon curd over the marzipan, then place a lemon sponge in the centre, brushing a little lemon curd all over the sponge. Press a pistachio sponge beside it, then spread the sponge all over with lemon curd. Repeat with the other two rectangles on top, to form a check pattern, brushing all over with lemon curd to help the marzipan stick.

4 Bring the sides of the marzipan over the top of the cake, trimming any excess marzipan as needed, then turn over so that the seam is on the bottom. Press the ends of the marzipan to seal, then shape with your hands to smooth out any gaps or lines before serving.