Preheat the oven to 180°C Lightly grease the inside of three Ball & Kerr or Kilner 500ml jars.
Beat the sugar and margarine together with an electric whisk until pale and creamy then slowly beat in the eggs.
Gently fold in the flour and baking powder then, once mixed, place half the mixture in a separate bowl.
Add the food colouring to one bowl and gently stir in until completely combined. Mix the cocoa powder with the boiling water, add it to the other bowl and gently stir in until completely combined.
Spoon a 1cm layer of the pink mixture into the prepared jars and bake for 20 minutes without lids.
Remove from the oven, add a 2cm layer of the chocolate mixture and bake for a further 15 minutes.
Remove from the oven and add a top layer of the pink mixture then bake for a final 15 minutes.
Place jars on a wire rack to cool.
For the icing, beat the butter and sugar together with an electric mixer until smooth and pale. Whilst continuing to beat, gradually mix in the water and then the milk and beat until you reach a creamy consistency.
When the cakes are completely cooled, cover the tops with butter icing, replace the jar lids and eat within 2 days.
Tip: If storing for longer than 2 days, omit the icing.
Recipe thanks to Lakeland.co.uk