What makes this lightened up cake recipe healthier than boxed cake?

To make this healthier devil's food cake, I reduced the amount of cake mix, reduced the amount of butter and replaced some with unsweetened applesauce. I also used sweetener instead of sugar which doesn’t spike blood sugar levels as much.

Do I have to add the protein powder?

Nope! If you want to leave out, just replace with an extra 1/4 cup of flour.

How should I store chocolate frosting?

If you have any extra frosting, keep it stored in the refrigerator. Note that the frosting will stiffen up after being chilled, so it’s best to leave it out at room temperature for a bit if you plan on using it again. It won’t have the same texture as the original frosting, but it will be spreadable again.