Preheat the oven to 325°F (165°C).

In a 10-inch cast iron skillet or heavy oven-safe pan, melt 1/2 cup butter over low heat. Remove from heat and sprinkle brown sugar evenly over the melted butter.

Arrange pineapple slices over the sugar mixture, fitting them snugly. Place cherry halves in the center of each pineapple ring and in any open spaces.

In a medium bowl, sift together cake flour, baking powder, and salt. Set aside.

Separate eggs, placing whites in a large mixing bowl and yolks in a smaller bowl.

Beat egg whites on medium speed until soft peaks form. Gradually add white sugar, continuing to beat until medium-stiff peaks form.

Beat egg yolks until thick and lemon-colored. Gently fold yolks into the whipped egg whites.

Sprinkle the flour mixture over the eggs and fold gently until just blended.

Stir in vanilla extract, reserved pineapple juice, and 1 tablespoon melted butter.

Pour batter evenly over the arranged fruit in the skillet.

Bake 30–35 minutes, or until a toothpick inserted in the center comes out clean.

Let the cake cool for 5 minutes in the pan. Run a knife around the edges, then carefully invert onto a serving plate.

Serve warm or at room temperature.