My Google search for a cupcake-sized Pineapple Upside Down Cake resulted in quite a few recipes, surprisingly. The best one I found was from Allrecipes.com
I made a few minor adjustments*, but was very pleased that they not only turned out well the very first time, but they kept well (refrigerated) through the next day.
Pineapple Upside Down Cupcakes
1/2 cup butter, melted
1 1/2 cups brown sugar
24 maraschino cherries
1 to 2 cans pineapple rings
1 (18.25 ounce) package yellow cake mix (if you can find pineapple mix, that will work, too)
1 1/3 cups pineapple juice
1/3 cup vegetable oil
Move an oven rack into the middle of the oven. Preheat oven to 350 degrees. Spray 24 muffin cups with cooking spray. Line a work surface with waxed paper. Spoon 1 teaspoon melted butter into the bottom of each sprayed muffin cup. Spoon 1 tablespoon brown sugar in each muffin cup. Press a maraschino cherry into the center of the brown sugar in each muffin cup. Trim pineapple rings to fit around cherry. It's okay if it covers the cherry slightly.
Mix cake mix, eggs, pineapple juice, and vegetable oil in a large bowl with electric mixer on low speed until moistened, about 30 seconds. Turn mixer speed to medium and mix for 2 minutes. Pour pineapple cake batter into the muffin cups, filling them to the top; do not overfill.
Bake in the preheated oven until a toothpick inserted into the center of a cupcake comes out clean, about 20 minutes. Allow cupcakes to cool at least 5 minutes before inverting muffin cups onto the waxed paper to release. Serve with pineapple and cherry sides up.
*Adjustments: The original recipe called for a pineapple cake mix, which neither of my grocery stores carried. The pineapple juice adds plenty of flavor, though, so I think the yellow cake mix worked fine. You can, of course, make the batter from scratch if you prefer. The recipe also called for crushed pineapple, pressed into the top, but I prefer the chew of the rings. And finally, I've omitted the dusting of powdered sugar called for because these are quite sweet all on their own. If the rings or cherries stick, it's easy to pop them out with a plastic fork/knife and rearrange while the cakes are warm. They'll stay put once they've cooled.