Preheat oven to 325 degrees. Take melted ½ cup of butter and pour over bottom of a 10 inch cake pan. Sprinkle brown sugar over butter and lay out pineapple slices evenly. Sift together flour, baking powder, and salt. Separate the egg yolks and whites into two bowls. In one bowl, beat egg whites just until soft peaks form. Gradually add sugar, beating well after each addition. Beat until stiff peaks form. In another bowl, beat egg yolks at high speed until very thick and yellow. Gently fold egg yolks and flour mixture into whites until barely combined. Fold in the 1 tablespoon melted butter. Spread batter evenly over pineapple in pan. Bake for 30 minutes, and cool before flipping out of pan!