In a heat proof bowl placed over a bowl of simmering hot water, whisk the eggs and sugar to a smooth consistency.
Beat in the butter and whisk until a thick creamy mixture is attained. Cool this. Sift the flour, baking powder and baking soda and fold it into the butter mixture. Fold in the zest and juice finally.
Grease 2 ramekins and spoon the mixture in them. Double seal the ramekins with foil.
Place in a steamer ensuring that water reaches a third of the sides of the rameking. Steam for about an hour and cool and then unmould.
