Preheat oven to 350°F (175°C). Line a standard 12-cup muffin tin with paper liners. You are setting up the pan so the caramelized topping goes at the bottom and will end up on top after baking. Take 5 minutes.

Melt 1/2 cup unsalted butter in a small saucepan over low heat (2–3 minutes). The butter should be liquid but not bubbling. Divide the melted butter evenly into the bottom of each liner, using about 1 teaspoon per cup (2 minutes total).

Sprinkle 1 tablespoon packed brown sugar into each liner over the butter. The sugar will mix with the butter and create a caramel layer during baking (2 minutes).

Open one 20-ounce can of pineapple slices in juice. Drain the slices in a colander, collecting the juice in a separate measuring cup. Reserve 1/4 cup of the juice for the cake batter (1 minute).

Cut each pineapple slice in half (or into quarters if very large) so it fits inside the cupcake liner. Place one pineapple piece in the center of each liner, standing it upright or laying it flat (2 minutes).

Place one maraschino cherry in the center of each pineapple piece. This will be the top decoration when the cupcake is inverted. All 12 liners should now have butter, brown sugar, pineapple, and a cherry (1 minute). Checkpoint: Your muffin tin should look colorful with red cherries and yellow pineapple in each cup.

In a medium mixing bowl, whisk together 1 3/4 cups all-purpose flour, 1 1/2 teaspoons baking powder, and 1/4 teaspoon salt. Set aside (1 minute). This dry mixture prevents lumps in the cake.

In a large mixing bowl, add 1/2 cup softened unsalted butter and 3/4 cup granulated sugar. Using an electric mixer on medium speed, beat for 2–3 minutes until the mixture looks pale, fluffy, and lighter in color. Scrape down the bowl halfway through. Checkpoint: The mixture should look like wet sand or mousse, not dense and grainy.

Crack 2 large eggs into a small bowl. Add one egg to the butter mixture and beat on medium speed for 1 minute until fully blended. Add the second egg and beat for another 1 minute. The mixture should be smooth and slightly pale (2 minutes total). If it looks curdled or separated, add 1 tablespoon of the flour mixture to bring it together.

Add 1 teaspoon vanilla extract to the batter and mix on low speed for 30 seconds. Scrape down the bowl.

Add 1/3 of the flour mixture to the batter. Mix on low speed for 30 seconds until just combined (don't overmix). Scrape the bowl.

Add 1/2 of the reserved pineapple juice mixed with 1/4 cup sour cream (combine them first in a small cup). Mix on low speed for 30 seconds until just combined. Scrape the bowl.

Add the remaining 1/3 of the flour mixture to the batter. Mix on low speed for 30 seconds until just combined. Scrape the bowl.

Add the remaining sour cream and pineapple juice mixture to the batter. Mix on low speed for 30 seconds until just combined. The batter should be smooth but not overmixed (thin streaks of white are okay). Overmixing creates tough cupcakes. Checkpoint: The batter should be thick and creamy, pourable but not runny.

Divide the batter evenly among the 12 prepared liners, filling each about three-quarters full. Use a small cookie scoop or spoon to ensure equal portions. Each liner should have about 2 tablespoons of batter (2–3 minutes).

Place the muffin tin in the preheated 350°F oven on the middle rack. Bake for 18–22 minutes. The cupcakes are done when the tops are golden brown and a toothpick inserted into the center of a cupcake (avoiding the fruit) comes out clean or with just a few moist crumbs. The sides should pull slightly away from the liner. Checkpoint: Tops should be dome-shaped and light golden. If a toothpick still has wet batter, add 1–2 more minutes and check again.

Remove the muffin tin from the oven and place it on a heat-safe surface or wire rack. Let the cupcakes cool in the pan for exactly 5 minutes. This is important: too long and they stick; too short and they fall apart during inversion. Set a timer (5 minutes).

Working quickly, place a wire cooling rack or serving plate on top of the muffin tin. Hold the tin and rack together securely with oven mitts. Flip the entire tin upside down so the rack is now at the bottom and the tin is on top (1 minute). Checkpoint: You should hear/feel the cupcakes release from the liners.

Lift the muffin tin straight up and away from the cooling rack, leaving the cupcakes (still in their liners) sitting upside down on the rack. Peel away the paper liners from the bottom of each cupcake, revealing the caramelized pineapple and cherry top (2–3 minutes). Be gentle so the topping doesn't stick to the liner.

Allow the cupcakes to cool completely on the rack for at least 30 minutes. The caramel will harden as it cools. Do not stack until fully cooled or the frosting (if using) will melt or the caramel will stick together. Checkpoint: Cupcakes should be room temperature and the caramel should feel firm to the touch.