Preheat the oven to 375 degrees F. In an ungreased 9-inch round cake pan, melt the butter over low heat or in the oven, then stir in the brown sugar until combined. Arrange the pineapple slices over the sugar in a single layer, with one slice in the center and the rest fitted around it to follow the curve of the pan. Set aside.

In a large bowl, beat the egg yolks until thick and lemon-colored. Gradually add the sugar, beating well. Blend in the vanilla and reserved pineapple juice. In a separate bowl, combine the flour, baking powder, and salt. Add the flour mixture to the egg mixture, beating well.

In a small bowl with clean beaters, beat the egg whites on high speed until stiff peaks form. Fold into the batter. Spoon the batter over the pineapple in the pan.

Bake for 35 to 40 minutes, or until a toothpick inserted in the center comes out clean. Let stand 10 minutes before inverting onto a serving plate. Place a cherry in the center of each pineapple slice.

TIPS:

• If using canned pineapple, drain the rings well and pat them dry with a paper towel before arranging them in the pan. Extra moisture thins out the caramel layer and keeps it from turning glossy and sticky.
• Invert the cake right around the 10-minute mark, not sooner and not much later. Too soon and the caramel is still scalding and the cake too fragile to hold together. Too late and the caramel starts to set against the pan, making the cake stick instead of releasing cleanly.