Lightly spoon flour into dry measuring cups; level with a knife. Sift together flour, baking powder, and salt. Combine sugar, 1 teaspoon vanilla, and eggs in a medium bowl, and beat with a mixer at medium speed until sugar dissolves. Add flour mixture to egg mixture; stir until well blended. Stir in apple, chopped walnuts, and raisins.
Spoon batter into an 8-inch square baking dish coated with cooking spray. Bake at 350° for 40 minutes or until golden brown and a wooden pick inserted in center comes out clean. Cut into 9 squares.
I really like these. They are not overly sweet or jazzed up; just a good, rustic recipe. Serve them with vanilla ice cream for dessert, then eat them plain for breakfast the next morning. The walnuts give complexity to the flavor.