Step #1 In a bowl whisk together the flour, the baking powder, & a pinch of salt & in another bowl stir this together the sour cream & the baking soda.
Step #2 In a large bowl cream together the butter & 1 c of the granulated sugar until the mixture is light & fluffy, add the eggs, beating well after each addition, 1 at a time, & beat in the vanilla.
Step #3 stir in the the flour mixture alternately with the sour cream mixture & stir the batter until it is mixd well.
Step #4 Pour the batter into a buttered 10-inch round cake pan.
Step #5 In a small bowl stir together the remaining 1/3 c granulated sugar, the brown sugar, and the cinnamon & swirl the sugar mixture into the batter.
Step #6 Bake the cake in the middle of a preheated 350°F.
Step #7 oven for 45 to 50 mins, transfer it to a rack, or until a tester comes out clean, & let it cool.