Plum Upside-Down Cake

Ingredients

• 9 tablespoons (1 stick plus 1 tablespoon) unsalted butter, room temperature
• 1 cup packed light-brown sugar
• 4 red plums (about 1 pound) halved and pitted, each cut into 12 wedges
• 1 large egg
• 1/2 cup reduced-fat sour cream
• 1 cup all-purpose flour (spooned and leveled)
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1 1/2 teaspoons pumpkin-pie spice
• 1/3 cup finely chopped walnuts
• Whipped cream (optional)

Instructions

1. 1
   Preheat oven to 325 degrees. Place 3 tablespoons butter in an 8-inch round cake pan; melt in preheating oven, about 4 minutes. Sprinkle melted butter with 1/2 cup brown sugar. Arrange overlapping plum wedges in a circle around edge of pan; repeat in center, covering bottom of pan. Set aside.
2. 2
   In a large bowl, beat together remaining 6 tablespoons butter, remaining 1/2 cup sugar, and egg. Beat in sour cream until blended. Set aside.
3. 3
   In a medium bowl, mix together flour, baking soda, salt, pumpkin-pie spice, and walnuts. Stir flour mixture into sour-cream mixture until just combined (batter will be thick).
4. 4
   Spread batter evenly over plums. Bake until a toothpick inserted in center of cake comes out clean, about 50 minutes. Cool in pan 5 minutes. Run a knife around edge of pan; invert onto a serving plate. Serve warm or at room temperature, with whipped cream if desired.