Beat together the butter and 1 cup (250 ml) of the sugar until light and fluffy. Add the eggs, sour cream, and vanilla, and beat until well blended. Add the flour, baking powder, and baking soda and mix until thoroughly combined. Make the topping by combining the remaining sugar, brown sugar, cinnamon, and optional nuts. Pour half the batter into a greased 10-inch (25 cm) tube or Bundt pan. Sprinkle 2/3 of the topping over the batter, and add the remaining batter. Top with remaining topping mixture and bake in a preheated 325 (160C) oven for 60 minutes, or until a toothpick inserted in the center comes out clean. Serves 8 to 10.