Place butter in a small saucepan and heat over low heat until butter is melted.
Add butter, milk, eggs and vanilla to flour and sugar mixture.
Stir with a wooden spoon until well combined.
Pour into a square baking dish lined with parchment paper (note 3)
Bake 30 -35 minutes, or until golden brown.
Poke the middle with a sharp knife, if it comes out clean the cake will be cooked.
Cool on a wire rack.
Once cooled, cut the cake in half using a sharp knife.
Evenly spread raspberry jam over bottom layer of cake, making sure it comes out to the edges without over flowing.
Place top half of cake on jammed half.
Dust with sifted icing sugar and serve.
Notes
note 1 - if you don't have self-raising flour, add 2 teaspoons of baking powder to 6oz of all purpose flour and that should aid the cake in rising. note 2 - if you're in Australia, caster sugar is best. In America, regular granulated sugar is fine. note 3 - I use a square 8inch square glass pyrex dish and just roughly place parchment paper in it to line it. It's much easier. If you wanted a fully spuare cake, I'd cut out paper for the bottom and the sides and grease the pan to make it stick.