PREHEAT oven to 350° F. Grease 13 x 9-inch baking pan.
COMBINE flour, baking powder, cinnamon and nutmeg in medium bowl. Beat granulated sugar and butter in large mixer bowl until creamy. Beat in eggs and vanilla extract until smooth. Alternately beat in flour mixture and evaporated milk. Stir in apples and pecans. Spread batter into prepared baking pan.
BAKE for 40 to 45 minutes or until wooden pick inserted in center comes out clean. Cool in pan on wire rack for 20 minutes. Cut into bars. Dust with powdered sugar before serving and top with pecan halves, if desired.