Heat oven to 350°F. Grease 9-inch square pan with shortening or cooking spray. In large bowl, beat 1 1/2 cups of the brown sugar and 1/2 cup butter with electric mixer on medium speed 2 minutes or until creamy. Beat in egg. In small bowl, mix 2 cups of the flour, the baking powder, allspice and salt with whisk. On low speed, add flour mixture to butter mixture, beating just until blended; fold in sour cream and apples. Spread batter in pan.