Heat oven to 350ºF. In 9-inch square pan, melt 1/4 cup butter in oven. Stir in brown sugar and corn syrup; spread evenly in pan. Arrange pineapple slices on brown sugar mixture; place cherry in center of each pineapple slice.
Note: Do not use 8-inch square pan as there will be too much batter and it will not bake all the way through.
In a bowl, beat cake mix, 1/2 cup butter, water, vanilla and eggs on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour batter over pineapple and cherries.
Bake 38-43 minutes or until surface is golden brown.
Immediately run knife around side of pan to loosen cake. Place heatproof serving plate upside down onto pan; turn plate and pan over. Leave pan over cake 5 minutes so brown sugar topping can drizzle over cake. Carefully remove pan; cool 30 minutes. Serve warm or cool. Store covered in refrigerator.