It hills up in the center, does it? You're baking at too high a temperature. If the outside of something gets overcooked while the center is underdone, it is a case of too much heat too fast. It is a chronic problem beginning grillers face, and often results in chicken that is scorched on the outside and uncooked in the middle.

It is no different with cakes, which tend to be quite delicate. Indeed, there are some cakes, especially cheesecakes and flourless cakes, that are cooked in a water bath (where the cake pan sits in a larger pan of water in the oven) to moderate the temperature and bake it very gently. If you're making a fairly traditional flour-based layer cake, though, you don't need a water bath. Just keep the oven temperature to 350°F (175°C) or less, and it will probably take 25 to 30 minutes to bake. If you continue to have problems, get an oven thermometer to check the accuracy of your oven temperature.

And for the record, its normal for most cakes to rise in the middle as they bake.