In a small bowl mix together the melted butter and brown sugar.
Spread the butter/brown sugar mixture evenly on the bottom of the crock-pot dish.
Drain the pineapple juice into a cup. Set aside for the cake mix.
Arrange the pineapple slices on the brown sugar mixture cutting them as needed to fit in one layer without overlapping the slices of pineapple.
Add a cherry in the middle of each slice.
In a large mixing bowl mix together the cake mix according to the box substituting the water with the pineapple juice that you reserved from the can of pineapple slices. If you do not have enough pineapple juice, add water until you have enough.
Pour the cake batter over the pineapples evenly.
Cover and cook on HIGH for 3 to 3 1/2 hours or until a toothpick inserted into the middle comes out clean.