Drain pineapple and reserve juice for cake batter.
Grate butter and add brown sugar and pineapple. Stir till combined.
Place 2 TBSP of pineapple mixture in each muffin tin.
Add a maraschino cherry to the center of each.
Make cake batter by combining cake mix, eggs, butter,milk, reserved pineapple juice and vanilla in your mixing bowl.
Beat on medium speed 3 minutes or so until combined.
Use batter to finish filling each muffin tin.
Bake on 350 degrees 30-35 minutes or until toothpick tests clean.
Let stand on cooling rack 10 minutes. Run knife around each one and pop out with spoon.