Preheat the oven to 200C/400F/gas mark 6
Use two 23cm/9 inch sandwich tins.
Sift the flour and baking powder into a bowl, add the sugar and mix well by lifting and sprinkling, using a spoon. Put the margarine to melt in a small saucepan over a low heat. Remove from heat as soon as it's melted.
Put the hot water in a jug together with the malt extract and set aside. Finely grate the lemon rinds, add to the dry ingredients and mix in by lifting and sprinkling as before. Squeeze the lemons, add the juice to the water and malt mixture and stir until the malt has completely dissolved.
Preheat the oven and prepare the sponge tins by lightly greasing and flouring them. As quickly as you can, add the melted margarine to the dry ingredients and stir well in, followed immediately by the water, malt and lemon juice mixture. Beat well for a few moments only before transferring equal amounts to each of the two prepared sponge tins and placing them in the preheated oven. Bake till the top goes firm and golden brown (about 20-25 minutes), or test with a warm knife. Allow to cool before removing from the tins.