Preheat the oven to 350ºf. Butter the baking dish. Put 2 1/2 oz of the orange juice and 2 1/2 oz of the marmalade into a small saucepan and set aside for the glaze.
Put all the other ingredients for the pudding batter into a food processor, process them and then pour and scrape the batter into the buttered dish, smoothing the top.
Place in the oven and cook for about 40 minutes — though give a first check after ½ hour — by which time the sponge mixture will have risen and a cake tester will come out cleanish. Remove from the oven and leave in the dish.
Warm the glaze mixture in the pan until melted together, then paint the top of the sponge, letting the chunks or slivers of peel be your sole, unglinting decoration on top of the mutely gleaming pudding-cake. Know that this sponge will keep its orange-scented warmth for quite a while once out of the oven,
Use a large spoon or cake slice to serve, and put a jug of heavy cream on the table.