Preheat the oven to 350 degrees F.
Grease and line the bottom of a 9-inch round cake pan (preferably a springform pan) with parchment paper.
Melt and stir together the butter and brown sugar and pour into the cake pan. The brown sugar doesn't have to be completely dissolved.
Prepare 7 pineapple slices by patting them completely dry with a paper towel.
Lay one whole pineapple ring in the center of the brown sugar mixture.
Cut 6 pineapple slices in half and around the center pineapple slice on top of the brown sugar mixture.
Place a maraschino cherry in the center of each pineapple ring. Set the pan aside.
In a large mixing bowl, cream the sugar and butter until light and fluffy.
Add 1 egg and mix.
Mix in milk, yogurt and vanilla.
Stir in flour, baking powder, and salt until just combined.
Fold in walnuts
Pour the cake mixture evenly over the pineapples in the pan. It’s a thick cake batter, so it helps to dot the batter over the pineapples and carefully spread it to the edges.
Put the pan in the oven and bake for 45 or 50 minutes, or until a toothpick inserted in the center of the cake comes out clean.
Let sit for about 5 minutes.
Loosen the sides with a knife, then turn upside down onto a flat serving dish. (The pan should still be warm when you do this).
Serve with vanilla or maple walnut ice cream.