This Chocolate Orange Marble Cake is what happens when two of my favourite flavours refuse to pick a side. Chocolate and orange just make sense together — one rich and deep, the other bright and citrusy — and instead of choosing one for this loaf, I let both share the same tin. Half the batter turns citrusy and bright with orange zest, the other half goes rich and dark with melted chocolate and cocoa. Spoon them into the pan in turns, run a knife through in loops, and the oven takes care of the rest, giving you those swirls every single time without much effort on your part.