Caramel Walnut Upside-Down Banana Cake

Spray a 9-inch round cake pan with 2-inch-high sides with nonstick spray.

For the topping, bring butter, sugar, and corn syrup to a boil in a medium saucepan, stirring constantly until the butter melts. Boil syrup for 1 minute.

Stir in walnuts and spread topping in the prepared pan. Let topping cool completely.

Preheat the oven to 350°F.

For the cake, sift the first four ingredients (cake flour, baking powder, baking soda, salt) into a medium bowl.

Using an electric mixer, beat butter and both sugars in a large bowl until blended.

Beat in eggs one at a time, then add mashed bananas, sour cream, rum, and vanilla.

Beat in dry ingredients in two additions just until combined.

Spoon batter into the pan over the cooled topping.

Bake the cake until a tester inserted into the center comes out clean, about 40 to 45 minutes.

Cool cake in pan on a rack for 15 minutes.

Cut around the cake to loosen it. Place a platter over the pan and, holding pan and platter together, turn over.

Let the cake stand for 5 minutes, then gently lift off the pan.

Cool the cake for at least 15 minutes for topping to set.

Serve warm or at room temperature with whipped cream or vanilla ice cream.