Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment if desired.

In a small saucepan or bowl, melt 4 tbsp unsalted butter and stir in 1/2 cup brown sugar until smooth. Pour this mixture into the prepared pan.

Place 12 pineapple slices in a single layer over the caramel and place a maraschino cherry in the center of each ring.

In a bowl, whisk together 1 1/2 cups flour, 1 tsp baking powder, 1/4 tsp baking soda, and 1/4 tsp salt.

In a separate bowl, cream 1 stick unsalted butter with 3/4 cup granulated sugar until light. Add 2 room-temperature eggs one at a time, mixing well. Stir in 1 tsp vanilla extract and the reserved 1/4 cup pineapple juice.

Mix in 1/4 cup sour cream and 1/3 cup milk until smooth.

Gradually fold the dry ingredients into the wet mixture until just combined.

Pour the batter evenly over the arranged pineapple and cherries. Smooth the top gently. Bake for 30–35 minutes, or until a toothpick comes out clean.

Let the cake cool in the pan for 8–10 minutes, then invert onto a serving plate.

Allow the cake to sit for another 10–15 minutes to let the caramel set slightly. Serve warm or at room temperature.