Preheat oven to 350°.
Press 9 pineapple slices between paper towels until barely moist; set aside. Reserve the remaining pineapple for another use.
Coat a 9-inch square baking pan with cooking spray; drizzle caramel topping over bottom of pan. Arrange prepared pineapple slices in a single layer over caramel; place 1 cherry in the center of each slice.
Place the butter in a large microwave-safe bowl. Cover and microwave at high 1 minute or until the butter melts. Add sugar, stirring with a whisk. Add eggs, and stir well. Stir in low-fat buttermilk and next 4 ingredients (buttermilk through baking soda). Lightly spoon 1 1/4 cups flour into dry measuring cups, and level with a knife. Add flour, stirring just until blended (do not overstir). Pour the batter into prepared pan.
Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool for 1 minute in pan on a wire rack. Place a plate upside down on top of the cake, and invert onto plate. Cool completely. Cut cake into squares.