The High Rise Glorious Skittle Skat Roarious Sky Pie Angel Food Cake by Nancy Willard, illustrated by Richard Jesse Watson (Harcourt, 1990).
This was a childhood favorite of mine. The girl in the story wants to bake a special cake for her mother's birthday-- a cake that her grandmother baked for her when she was a little girl. When the girl searches the attic for the recipe, she finds it, except there is one secret ingredient missing. Luckily, a trio of angels show up in her kitchen to help her make the most delicious, heavenly cake ever.
I found this to be a magical story as a kid. Reading it again now, I'm especially impressed with the illustrations, which are extremely creative and layered. It's also nice that the angels are diverse in race (white, black, and Asian), gender, and age.
Most of all, you will find your mouth watering for angel food cake after reading this book!