PREHEAT oven to 375°F. Mix flour, baking powder and salt; set aside. Beat butter and 1-1/2 cups of the sugar in large bowl with electric mixer on medium speed until light and fluffy. Blend in eggs and vanilla. Add flour mixture alternately with milk, mixing well after each addition.
POUR into greased 13x9-inch baking pan; top with apples. Mix remaining 1/4 cup sugar and the cinnamon; sprinkle over apples.
BAKE 35 to 40 min. or until toothpick inserted in center comes out clean. Cut into 16 squares to serve.