In a saucepan, melt 2/3 cup butter; stir in brown sugar. Spread in the bottom of an ungreased heavy 12-in. ovenproof skillet or a 13x9-in. baking pan. Arrange pineapple in a single layer over sugar mixture; place a cherry in the center of each slice. Sprinkle with pecans and set aside.
In a large bowl, cream sugar and remaining butter until light and fluffy, 5-7 minutes. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla. Combine the flour, baking powder, baking soda, salt, cinnamon and nutmeg; add alternately to batter with buttermilk, beating well after each addition.
Carefully pour over the pineapple. Bake at 350° until a toothpick inserted in the center comes out clean, about 40 minutes for skillet, 50-60 minutes for baking pan. Immediately invert onto a serving platter. Serve warm.