In bowl, combine flour with sugar; with pastry blender, cut in butter until crumbly. Press into 9-inch (2.5 L) square cake pan; bake in 350°F (180°C) oven for 15 minutes.
Topping:
In bowl, mix together butter and eggs; blend in sugar, flour, baking powder, vanilla and salt. Stir in raisins; pour over base.
Bake in 350°F (180°C) oven for 20 to 25 minutes or until top springs back when lightly touched. Let cool on rack. (Make-ahead: Wrap and refrigerate for up to 4 days or overwrap in heavy-duty foil and freeze for up to 2 weeks.) Cut into squares.