Question:

It was my husband’s birthday this last weekend and he wanted a homemade Spice Cake. I found an amazing recipe and it called for both baking soda and baking powder. Why use both of those ingredients in a recipe? (The cake came out wonderful, btw…)

Answer:

Basically, the reason for both is because sometimes you need more leavening than you have acid available in the recipe. It's all about balance. Another reason to use both baking powder and baking soda is because they affect both browning and flavor.