Melt 4 tablespoons butter in a 10-inch cast-iron skillet. Sprinkle brown sugar evenly; arrange pineapple with one cherry in each center.

Whisk flour, baking powder, and salt in a bowl.

Beat remaining butter and granulated sugar until fluffy. Beat in eggs and vanilla; alternate adding flour mixture and milk.

Carefully spread batter over fruit without disturbing pattern.

Bake at 350°F for 35 to 40 minutes until tester in cake comes out clean. Cool 10 minutes; invert onto plate.