Cake 

• Preheat your oven to 160ºC/140ºC fan. Line your baking tins (I use 2 x 20cm round sandwich tins) with baking parchment or reusable baking liners.
• Finely grate the zest of two lemons.
• Sift the self-raising flour (225g) and baking powder (2 tsp) into a large bowl. Add the remaining ingredients (4 medium eggs, 225g soft margarine or butter, 225g caster sugar, grated lemon zest and 2 tsp milk) and beat (with an electric mixer on a slow speed or by hand) until combined. Make sure that there are no small lumps of butter/margarine in your mixture. If there are, beat for a little longer until the mixture is smooth.
• Split the mixture equally between the pre-prepared tins. Use the back of a spoon to spread the mixture evenly in the tins.
• Bake for 30-35 minutes. To check if the cake is cooked insert a skewer into the centre and if it comes out clean the cake is ready.
• Leave the cake to cool in the tins for about 10 minutes. Remove them from the tins and then move them to a wire rack to cool completely – Make sure the cake has cooled completely before decorating.
• For the Icing - Beat the butter (125g) on a low speed until it is soft. Add the icing sugar (250g) and beat until combined - alittle at a time. Add zest and lemon juice.  Check the consistency of your buttercream - It should be soft enough that you could spread it onto a slice of bread without the bread tearing, but not runny. If it is a little stiff, then add a little milk (again no more than 1 tsp at a time) until is it the right consistency.