There are few possible reasons for a cake to have a hump and/or is cracked on top.

1. Too much of raising agent in the cake. Make sure of measuring the ingredients precisely and/or check the recipe.
2. Your cake pan was too small for the recipe. Use a larger pan.
3. The temperature of the Oven was too high causing the top to cook faster in a shorter span leading to uneven cooking. Use Oven thermometer.
4. The cake was baked on too low or high of a rack. Cakes are better baked in the middle of the oven.
5. Opening the Oven door frequently. This causes temperature in the oven to drop causing uneven cooking.

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1. Cake Recipes
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