Combine flour and baking powder. In a large bowl, mix sugar, mayonnaise and vanilla until well-blended. Stir in flour mixture and 1/2 cup pecans. (Dough will be thick and sticky.)

Press into well-greased 8-inch square baking pan. Sprinkle with the remaining pecans, press into dough. Bake in preheated 350 degree oven 15 minutes or until pick inserted in center comes out clean. Cool in pan on rack. Cookies are soft while hot but firm when cool.
Yield: 12 squares