I was asked to create this cake for a friend of a friend. All I knew was that it had to be fruity, bright, and the person was from Brazil. So I quickly settled on a lime sponge, sandwiched with mango and passionfruit curd, but needed to come up with a decorating plan. That’s when I thought of the colours of the Rio Olympics, which were popping up on my tv on repeat. I wasn’t sure how to incorporate them all at first, until I had a little flash of inspiration to pipe the different colours in a sort of wreath round the top. It’s a really simple but effective technique, so if you’d like to give it a try then read on.