3/4 cup firmly packed light brown sugar
1/4 teaspoon baking soda
4 teaspoons ground cinnamon
1/4 teaspoon salt
11 tablespoons unsalted butter
1 cup granulated sugar
2 1/2 teaspoon vanilla extract
2 large eggs
2 cups unsifted bleached all-purpose flour
1 cup sour cream
1 teaspoon baking powder
Confectioners’ sugar for sifting over the baked cake
Preheat the oven to 350 degrees F.
Film the inside of a nine-inch springform pan (2 3/4 inches deep) or a round 9-inch cake pan (3 inches deep) with nonstick flour-and-oil spray.
If you are using the 9-inch cake pan, line the bottom of the prepared pan with a circle of ovenproof parchment paper, then film the surface of the paper and the sides of the pan with the spray.
For the filling and topping, thoroughly combine the brown sugar and cinnamon in a bowl. Turn half of the mixture into another bowl, drizzle over the melted butter (3 tablespoons) and vanilla extract (1/2 teaspoon), and combine until the sugar is moistened
The buttered mixture will look like clumpy, damp sand. Set both mixtures aside.
For the batter, sift the flour, baking powder, baking soda and salt onto a sheet of waxed paper.
Cream the butter (8 tablespoons) in the large bowl of a freestanding electric mixer on moderate speed for 2 minutes. Add the granulated sugar in 2 additions, beating for 1 minute after each portion is added.
Beat in the eggs, one at a time, mixing for 45 seconds after each addition. Blend in the vanilla extract (2 teaspoons). On low speed, beat in half of the sifted ingredients, the sour cream then the remaining sifted ingredients.
Scrape down the sides of the mixing bowl with a rubber spatula to keep the batter even-textured. The batter will be thick but creamy-textured.
Spoon a little more than half of the batter into the prepared baking pan. Sprinkle over the unbuttered sugar-cinnamon mixture. Spoon the remaining batter on top in dollops and smooth the top with a palette knife or rubber spatula.
If you wish, swirl the batter, using the tip of a rounded table knife or small off set palette knife. Sprinkle the buttered sugar-cinnamon mixture over the top.
Bake the cake in the preheated oven for 45 minutes, or until set and a wooden pick withdraws clean when tested about 2 inches from the center of the cake. The baked cake will pull away slightly from the rounded edges of the baking pan.
It will have a craggy, uneven surface, and this is to be expected. Completely cool the springform-baked cake in the pan on a cooling rack, then unclasp the outer ring of the pan, leaving the cake on its metal base.
Cool the cake in the round cake pan in the pan on a cooling rack for 10 minutes. Invert the cake onto another cooling rack, lift off the pan, peel off the bottom circle of parchment if it has adhered, and invert again to cool right side up.
Just before slicing into thick wedges and serving, sift confectioners’ sugar over the top of the cake, if you wish.