Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly. Drain the canned pineapple slices, reserving ¼ cup of the juice for the batter. Cut the pineapple slices into smaller rounds to fit the bottom of each cupcake liner.
In a small bowl, stir together the melted butter and brown sugar until combined. Spoon about 1 teaspoon of the brown sugar mixture into the bottom of each cupcake liner, spreading it evenly. Place a small pineapple round in the center of each liner. Add a maraschino cherry in the middle of the pineapple slice if desired.
In a large mixing bowl, combine the cake mix, reserved pineapple juice, vegetable oil, eggs, and vanilla extract. Beat with a hand mixer or whisk until smooth and well combined (about 2 minutes).
