Pre-heat the oven to 180°C (350°F).
Grease and line two 24cm (8 inch) round cake tins.
Beat the butter and sugar together until light and fluffy (I used my stand mixer, but you can do it by hand).
Add the eggs, one at a time, beating each one in before adding the next.
Sift the flour and baking powder together and then gradually add to the wet ingredients (I just kept my stand mixer running on the lowest speed).
Stop mixing when the flour is just incorporated (you may see a little flour that hasn't been mixed in, and that's okay).
Split the batter evenly between the two pans.
Bake for around 20-25 minutes (in the lower part of the oven), until the tops feel "bouncy" to the touch and an inserted skewer comes out clean.
Leave the cakes to cool in their pans for around ten minutes before turning out onto a wire rack. Let them cool completely before decorating.