In a bowl whisk together the flour, the baking powder, and a pinch of salt and in another bowl stir together the sour cream and the baking soda.

In a large bowl cream together the butter and 1 cup of the granulated sugar until the mixture is light and fluffy. Make sure you cream it well or the batter will be very thick. Add the eggs, 1 at a time, beating well after each addition, and beat in the vanilla.

Stir in the flour mixture alternately with the sour cream mixture and stir the batter until it is combined well.

Pour the batter into a buttered 10-inch round cake pan. In a small bowl stir together the remaining 1/3 cup granulated sugar, the brown sugar, and the cinnamon and swirl the sugar mixture into the batter. (If you have a very thick batter, layer it like an oreo cookie instead batter, cinnamon sugar in the middle, and batter on top.).

Bake the cake in the middle of a preheated 350°F oven for 45 to 50 minutes, or until a tester comes out clean. Transfer it to a rack, and let it cool.