Baking Obsession

Maybe it seems like the winter time dessert, but I bake it during any season. Use the fresh berries when they are available and the frozen ones when you can’t get them fresh.
Like the most of upside-down cakes, this one is moist, fragrant and a very good keeper.

For the topping:

• 1/2 stick (1/4 cup) unsalted butter
• 3/4 cup packed light brown sugar
• 1 3/4 cups fresh or frozen cranberries (do not thaw if frozen)
• 3/4 cup coarsely chopped walnuts, toasted

For the cake:

• 1 1/2 cups all-purpose flour1 1/2 teaspoons baking powder
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 stick (1/2 cup) unsalted butter, softened
• 3/4 cup granulated sugar
• 2 large eggs
• 1/2 teaspoon vanilla
• 3/4 cup well-shaken buttermilk
• Special equipment: a well-seasoned 10-inch cast-iron skillet

Make the topping:
Melt the butter in a skillet over moderate heat, and then swirl to coat a bottom and side of skillet and stir in the brown sugar. Simmer, stirring, until the sugar is dissolved, 1 to 2 minutes, then sprinkle the cranberries and walnuts evenly over the butter mixture and remove from heat.

Make the cake:
Put an oven rack in middle position and preheat the oven to 350°F.

Whisk together the flour, baking powder, baking soda, and salt. Beat together the butter and sugar in a large bowl with an electric mixer at high speed until light and fluffy, 4 to 6 minutes. Add the eggs, 1 at a time, beating well after each addition. Beat in vanilla. Reduce speed to low and add the flour mixture alternately in batches with the buttermilk, beginning and ending with the flour mixture and mixing until just combined.

Bake the cake:
Heat the topping in the skillet over moderately high heat until it starts to bubble, then gently spoon the batter over the topping and spread evenly. Quickly transfer to the oven; bake until the cake is golden brown and a wooden skewer comes out clean, 25 to 30 minutes. Cool the cake in the pan on a rack 15 minutes. Run a thin knife around inside edge of the pan, then invert a serving plate over the pan and invert the cake onto the plate. Cool completely on the plate on the rack, 1 hour. Serve the cake at room temperature.

Cake can be made a day ahead and kept wrapped or under a cake dome at room temperature.

Serve with lightly sweetened whipped cream.

Makes about 10 servings.