Some cakes need a long list of ingredients, a stand mixer and half your afternoon. This one needs a blender, four things you may already have, and about five minutes of effort. There’s no flour, no refined sugar, no dairy, no butter and no oil, yet it still comes out moist, fudgy and deeply chocolatey. The trick is overripe bananas, which provide sweetness and moisture, along with cocoa and eggs that give the cake its structure. It’s more of a dense, bittersweet chocolate cake than a fluffy sponge. Here’s how to make it, step by step.