Preheat oven to 325 degrees. Prepare 3-D Skeleton Casket pan with vegetable pan spray.
In medium bowl, combine flour, baking powder, cinnamon and salt; set aside. In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add eggs, one at a time, and vanilla; mix well.
Alternately add flour mixture and applesauce to butter mixture. Spread about 1/2 of cake batter so that it reaches the first horizontal line inside the pan. Sprinkle diced apples evenly over batter. Top with remaining batter, smoothing out the top.
Bake 58-62 minutes, or until toothpick inserted in center of cake comes out clean. Cool 15 minutes; remove from pan and cool completely on cooling grid.
Decorate cooled cake with Tip 5 and decorator icing.