Pre-heat the oven to 180°C (350°F). Grease and line two 8 inch round cake tins.
Beat the butter and sugar together until light and fluffy (I used a food processor).
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 keep the processor running). Stop working when the flour is just incorporated.
Split the batter evenly between the two pans and then bake for around 20-25 minutes, 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.
For the frosting: beat the butter and cream cheese together. Sift in the icing sugar and mix until well combined.
To assemble: turn one of the cakes over so that the top is underneath and then spread the jam over the flat surface. Spread the frosting over the other. Place them on top of each other and sprinkle with icing sugar.For the Eton Mess version: spread jam over the bottom of one cake. Spread half of the whipped cream over the bottom of the other cake. Place the other cake on top and slather on the remaining cream. Top with fruit and mini meringues, sprinkling a little broken meringue over the top. Add any other decorations you like (I put a couple of flowers on for the prettiness factor).