Rhubarb Upside-Down Cake
A hint of fresh thyme gives this rustic cake a faint herbaceous quality that complements the warmth of cardamom and ginger and the tang of rhubarb. Be patient when turning the cake out of the pan; it may take several minutes for it to fully release. The surprise ingredient in the batter (mayonnaise) is an old-school trick for creating a supermoist cake. A dollop of Greek yogurt cuts through the richness of the cake—but you can omit it if you’d like.