Cakes made from a boxed mix can taste great, but their texture can be a little crumbly. Here's an easy way to firm them up and make them denser.
How to Make a Box Cake Denser
Preheat oven to 350°F and lightly coat the bottom of the cake pan with oil. (You can also use cooking spray or dust the pan with flour.)
Combine cake mix and instant pudding mix in a large bowl. Add 1/2 cup whole milk (can also use water), 1/3 cup oil, and 4 eggs into mixture.
Most box cake recipes call for 1/2 or 1/3 cup oil, so the amount of oil is slightly less or around the same. But the amount of water is greatly reduced in this recipe. Most box cake recipes instruct you to use 1 and 1/4 cups of water, and this recipe calls only for 1/2 cup. Whole milk is a recommended substitute for water because it has a thickening effect, but water will still work. The pudding mix and extra egg also produce firmer results.
Blend all ingredients together in the bowl, using either a stirring utensil or a mixer. Blend until the mixture is smooth and has no lumps. It will be thicker than most box cake mixes at this point.
Pour the mixture into your greased or floured pan. It may not pour easily; use a utensil to spread it evenly in the pan.
Bake according to the instructions on the box. (Typically 25 to 35 minutes for a 13" x 9" pan.)
Check on the cake periodically after 25 minutes of bake time. Use a toothpick or fork to poke the center of the cake. If it comes out clean, the cake is ready to come out of the oven. If not, let it continue to bake and keep checking on it.
When the cake is ready, remove it from the oven, let it cool, and decorate with icing (if desired). Then cut, serve, and enjoy a firm piece of box cake!