Heat oven to 350°F. Spray 9-inch square pan with cooking spray. In small bowl, beat 1/2 cup butter, 1/4 cup granulated sugar and the vanilla with electric mixer on medium speed until well blended. On low speed, beat in 1 cup flour until soft dough forms. Press dough in bottom of pan. Bake 10 to 15 minutes or until center is set.