Preheat oven to 180 degrees C. Grease and flour a 20x30cm pan. Sift together the flour, baking powder and salt. Set aside.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Beat in the flour mixture alternately with the milk and hot water, mixing just until incorporated. Stir in the raisins.
Pour batter into prepared pan. Bake in the preheated oven for 60 minutes, or until a toothpick inserted into the centre of the cake comes out clean. Allow to cool.