Heat the oven to 400 degrees F. Lightly coat the pan with butter and dust with flour. Sift the flour, baking powder and salt into a large mixing bowl. Beat in the butter until the mixture resemble coarse sand. Beat in the sugar then eggs one at a time. Add vanilla and milk and beat on until well blended. Pour into the prepared pan and bake until a knife inserted in the middle comes out clean (30 - 35 min). Cool on a wire rack for 5min.