Melt butter in a 10-inch cast-iron skillet over medium heat, and sprinkle with brown sugar. Arrange fresh pineapple slices, dried cherries, and macadamias over brown sugar; cook until sugar is bubbly and pineapple is browned.
Remove from heat.
Beat egg yolks until thick and pale; gradually add sugar, beating well.
Combine flour, soda, and salt; stir in cardamom, if desired.
Add to yolk mixture, beating just until blended. Stir in milk.
Beat egg whites until stiff but not dry; fold into batter, and spoon evenly over fruit.
Bake at 375 for 35 minutes or until a wooden pick inserted in center comes out clean. Run a knife around edge of cake to loosen; cool in pan on a wire rack 10 minutes. Invert onto serving plate.
