Lightly grease a 900ml (1 ½ pt) pudding basin. In a bowl, cream together the margarine and sugar until pale and creamy. Whisk in the eggs and stir in the Marzipan, cherries and Almond Extract.
Sift the flour and Baking Powder on top and carefully fold into the cherry mixture. Spoon into the prepared basin and smooth the top. Top the pudding with a round of baking parchment, and then cover the top of the basin with foil. Secure with string.
Either place the pudding in a steamer above a saucepan of boiling water or stand the pudding on a trivet inside a large saucepan and pour in sufficient boiling water to come halfway up the side of the basin. Cover tightly with a lid and steam for 2 hours, topping the water level up as required, until the pudding is risen and a skewer inserted into the centre comes out clean.
Towards the end of cooking time, make the sauce. Put the jam in a small saucepan and blend into a paste with 150ml (¼ pt) cold water. Blend the Ground Arrowroot with 30ml (2 tbsp) cold water and stir into the jam mixture. Stirring all the time, heat the sauce gently until it boils, thickens and clears.
To serve, unwrap the pudding and invert on to a warmed serving plate. Serve warm with the hot cherry jam sauce.