Preheat the oven to 170°C. Grease a large ovenproof dish with non-stick spray.
1. Pudding: Sift the flour, salt and baking powder together. In a separate bowl, beat the butter and sugar until light and creamy. Add the eggs one by one, mixing well after each addition. Add the marmalade or jam, zest and vinegar and mix well.
3. Dissolve the bicarbonate of soda in the milk. Alternate adding the milk mixture and the flour mixture to the batter. Transfer to the ovenproof dish and bake for 40-45 minutes or until done.