Rose - from Castro Valley, CA
A number of things could be going wrong. First, check your oven temperature. If the oven is too hot, the cake could be rising too quickly, causing the surface to crack. Overmixing can incorporate too much air into cake batter, again, causing your cake to crack as the air escapes while the cake bakes. Finally, if you are making a "from scratch" recipe, be sure you are measuring the ingredients correctly – too much shortening, baking powder or sugar can cause cracking; likewise, too many dry ingredients in relation to the amount of wet ingredients can cause cracking.