Grease and line two 21cm/8inch cake tins.
Put the oven shelves above each other, as close together as the cake tins will allow, in the middle of the oven.
Pre-heat the oven to 180°C.
Crack the eggs into a small bowl and beat lightly with a fork.
Place the butter and sugar in a large bowl and, using an electric whisk, whisk together until light and fluffy. This should take a couple of minutes.
Using a wooden spoon beat in the eggs one at a time.
Sift in the flour and baking powder and fold in using a large metal spoon. You want the mixture to drop off your spoon easily. If it looks too thick then add the milk. Try not to overmix.
Divide the mixture between the tins as evenly as you can and smooth the tops using a spoon or spatula.
Place each cake, one above the other, in the centre of the pre-heated oven, and leave to cook for 25 minutes until the top is golden and the cake springs back when you press it.
Leave to cool in the tins for ten minutes then turn out and cool on a wire rack.