Whether you use a cake mix or make a cake from scratch, you can take a few steps to make sure your cake is moist and tender. To prevent a moist and tender cake from falling apart, let it cool in the pan long enough to become firm before you turn it out of the pan. Chill the cake in an air-tight wrapping before you frost it.
Substitute a fruit puree, such as applesauce, pumpkin puree, mashed ripe bananas, canned crushed pineapple or plum puree for half the oil or butter called for in the recipe. The fiber in the fruit puree helps to absorb moisture and retain it so the cake tastes moist. The cake will be a little more dense than one without a puree, but it will be moist. A slightly denser cake holds up to slicing and serving better than a very light cake.
Substitute 2 cups of pumpkin puree or applesauce for the water called for in a cake mix. Add the eggs and oil that the cake mix calls for. The batter will be thick, but that is all right. The finished cake will be moist and tender. Let it cool completely, according to the instructions on the package, before turning it out. If you try to turn out the cake too soon, it may crumble, break or stick to the pan.
Brush cooled cake layers with simple syrup made by simmering equal amounts of water and sugar in a saucepan until the sugar dissolves completely. This is a technique professional bakers use to keep cake layers moist, whether they make them from scratch or from a mix. After applying the simple syrup, apply a thin coating of frosting and let the frosting dry before putting on the final layer. The syrup keeps the layers moist and the light coating of frosting keeps the cake from falling apart when you finish decorating it.
Spread a moist filling, such as whipped cream or creme anglaise, between cake layers. The moisture in the filling will help keep the cake moist. Cover the cake and store it in the refrigerator to prevent it drying out and to prevent spoilage of the filling. A chilled cake cuts more easily without falling apart.