Answers:
This happen because the sides cook faster than the middle, as they are within constant contact next to the hot vessel. As the sides set, the leaveners verbs to push the almost center sophisticated, cause a dome and/or a crack across the top from the pressure. The center sets end during baking.
Other Answers:
what lovey said. to stop this from occurring (as much) use the spatula and put more batter on the sides than surrounded by the middle (it isn't an exact item, in recent times push it from the middle to the side). It help for a while, but i devise it is better to only bring a blade and cut bad the dome beforehand frosting.