1 1/2 c. all-purpose flour
1 1/2 tsp. double acting baking powder
1 c. sour cream
1 tsp. baking soda
1 stick (1/2 c.) unsalted butter, softened
1 1/3 c. granulated sugar
2 lg. eggs
1 tsp. cinnamon
1 tsp. vanilla
1/3 c. firmly packed light brown sugar

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; 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.

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