Heat oven to 350. Butter the bottom and sides of a 9x13" pan. Melt 1/2 c. butter in saucepan and add 1 c. brown sugar. Bring to a boil, stirring frequently. Pour into prepared pan. Drain pineapple rings, reserving 1/2 c. juice. Arrange 12 pineapple rings in the butter/sugar sauce.
In a medium bowl whisk together flour, baking powder, salt, and nutmeg. In a large bowl, beat softened butter, sugar, and a 1/2 c. brown sugar with electric mixer on medium speed for 2 minutes, scraping occasionally. Add eggs, beat until combined. On low speed, beat in half the flour mixture. Pour in reserved 1/2 c. pineapple juice and the milk; beat until combined. Beat in remaining flour mixture and vanilla.
Spread batter carefully over pineapple slices in pan. Place one cherry in center of pineapple rings. Bake 35-40 minutes (until toothpick comes out clean). Cool in pan on wire rack for 10 minutes. Invert carefully onto serving dish. Serve warm, topped with yogurt or whipped cream if desired.