The gentle saute process caramelizes onion, making it sweet. The cake has no onion flavor, yet is rich, dense and extremely moist. Sweet onions are essential to the success of this recipe. Do not substitute standard yellow cooking (storage) onions. If you absolutely cannot bear the thought of a cake with onions, you may omit them and still have a deliciously rich and moist double chocolate cake.
This recipe is adapted from an old Williams-Sonoma book called “Muffins.” (The book has several recipes for quick breads in addition to the muffins.) It is by far my favorite recipe in the book and I make it a lot, often by request. In fact, this is a dern good cake. And did I mention that it’s easy? One bowl, ladies and gentlemen, one bowl. Need I say more?