What causes a sheet cake to sink in the center after it has baked and starts cooling? How can I prevent this from happening? —J.B., Lombard, IllinoisA sheet cake may rise and then sink after baking if the oven is not hot enough. If your cake sinks, check the accuracy of your oven temperature with an oven thermometer. If a cake hasn’t been in the oven long enough, it, too, will sink. To check for doneness at the end of baking time, insert a toothpick near the center of the cake. If the toothpick comes out clean, the cake is done. If the sides of the cake start pulling away from the pan, it is another indication that your cake is done. Other cake sinkers include undermixing the batter, moving the cake during baking, using a pan that’s too small for the amount of batter, and adding too much sugar or leavening or too little flour to the batter.