Preheat oven to 190°C / 170°C Fan / 375°F / Gas Mark 5. Line the base of two 20cm / 8-inch cake tins with parchment paper and grease the sides of the tin.
In a large mixing bowl cream the butter and sugar together for about 2-3 minutes until light and fluffy.
Add the eggs one at a time and beat well after each addition – if the mixture looks curdled, add a bit of the flour. Next mix through the vanilla extract.
Gently fold through the flour and mix until no lumps of flour remain. Add enough water/milk to loosen the cake batter slightly.
Evenly divide the cake batter between the cake tins, leaving a small dip in the centre of each cake to encourage even rising.
Bake the cakes for 20-30 minutes or until the tops have turned a light golden colour and a cake tester comes out clean.
Leave the cakes to cool in the tins for 10 minutes, then carefully run a knife around the sides of the tin and release the cakes from their tins.
Peel the parchment paper carefully off the base of each cake and leave the cakes to cool completely on a wire rack, base side down.
Once cool, fill the cake with raspberry jam and sandwich the two cake halves together.
Dust the top with icing sugar and serve.
