"Rip" Running Over The Top Of Cake

Some cakes are supposed to have a "rip" running over the top. If you like this to be nice and straight, run your finger along the middle of the cake batter once you've poured into the mould. Another solution for the braver ones amongst you: after a couple of minutes, just as the cake starts to rise, open the oven door and make a straight cut over the middle of your cake (lengthways). The rip will follow this cut.