Prepare pan – Pour melted butter into a 9-inch round pan or 9 x 13 dish. Sprinkle brown sugar evenly on top.
Arrange fruit – Place pineapple slices over the sugar layer. Put a cherry in the center of each ring. Cut pineapple slices in half if needed to fit.
Mix dry ingredients – In a small bowl, whisk flour, baking powder, and salt.
Make batter – In a large bowl, cream butter and sugar until fluffy. Beat in eggs, one at a time. Add sour cream, pineapple juice, and vanilla. Mix gently.
Combine – Fold dry mixture into the wet ingredients until smooth. Do not overmix.
Bake – Spread batter evenly over the fruit layer. Bake at 350°F (175°C) for 40–45 minutes, until golden brown and a toothpick comes out clean.
Cool and flip – Let cake rest for 10 minutes. Place a serving plate on top, flip quickly, and lift pan to reveal caramelized pineapple topping.