Preheat the oven to 180°C/350°F/gas mark 4. Use a double layer of foil to divide a 20 cm/8 in square cake tin in half. Line both sections with greaseproof paper.
Whisk together the butter and sugar until light and fluffy. Stir in the yoghurt, milk, vinegar and almond extract, then fold in the flour and baking powder.
Pour half of the batter into one of the halves in the tin. Mix drops of food colouring or beetroot juice into the remaining half of the batter until you get the desired shade of pink, then pour the pink batter into the other half of the tin.
Bake for 25 minutes until a skewer inserted into the centre comes out clean. Allow to cool for a few minutes in the tin before turning out onto a wire rack to cool completely. To decorate, gently transfer the cakes onto a chopping board and cut each one in half lengthways, trimming the edges to create straight and even layers.
Heat the marmalade in a small saucepan over a low heat until runny. Brush one long side of a pink strip of cake and one side of a yellow one and stick them together. Repeat to stick the other two strips together. Now paint the top of one pair completely with marmalade and place the other pair on top, with pink on top of yellow and vice versa to create a chequerboard pattern.
Dust a work surface with a little icing sugar and roll out the marzipan to a rectangle about 20 x 25 cm/8 x 10 in. Brush the outside of the cake with marmalade. Use a rolling pin to lift the marzipan over the cake and smooth it firmly around the top and sides, joining underneath. Trim away the excess and brush the seam with a little marmalade. Finish by pressing the edges together to create a seam at the bottom.