Desserts: Plum Upside-Down Cake Serves 8

1 T unsalted butter, plus extra for the pan;  all at room temp
6-7 firm, ripe plums, each cut into 8 wedges
1/4 cup granulated sugar
1 cup sifted cake flour (7/8 cup flour + 2 T cornstarch)
1 t baking powder
1/8 t kosher salt
3 eggs, separated
1 cup granulated sugar
5 T orange juice

Heat oven to 350F.  Butter 9-10" round pan and line bottom with parchment paper. Melt 1 T butter in large skillet over med-hi heat.  Add plums and 1/4 cup sugar and cook, tossing, until sugar dissolves and juices from the plums become syrupy, 3-4 minutes.  Arrange plums in pan in slightly overlapping concentric circles, starting from outside.  Spoon any pan juices over the top. 
Sift flour, bp, s together. Beat yolks until light, adding sugar gradually.  Add juice and sifted flour. Fold in stiffly beaten egg whites.  Pour batter over fruit.  Bake 375F 30-35 mins (I find it takes a bit more).  Turn upside down on serving plate.  Serve with whipped cream if desired.  Serves 8-10.