Most fluffy cake recipes come out of the oven with a raised, rounded top, which is referred to as doming. This can spell disaster for layered and/or decorated cakes.
Doming usually boils down to the cake pan or oven temperature. A pan that is too small for the batter inside can cause the middle of the cake to rise up.
Temperature is also crucial. Even if you set your oven to the temperature in the recipe, your cake pan might heat too quickly, resulting in an uneven baking job.
An easy way to help prevent doming is to always use a correctly sized cake pan. As for preventing doming in a too-hot oven, set your oven lower by about 10 degrees Fahrenheit.
If you wind up with domed cakes anyways, the simplest fix is to wait until the cake has cooled, and then use a large serrated knife to cut the excess off the top.