Preheat oven to 350°F (175°C). Grease and flour a 9-inch baking pan.
In a mixing bowl, cream together the butter and sugar until light and fluffy. Add eggs one at a time, beating well after each addition. Stir in vanilla.
In another bowl, whisk together flour, baking powder, and baking soda. Add to the creamed mixture alternately with sour cream, beginning and ending with the flour mixture. Mix just until combined.
Pour batter into prepared pan. In a small bowl, combine brown sugar, cinnamon, and nuts. Sprinkle over the batter.
Bake for 30 minutes or until a toothpick inserted into the center comes out clean. Cool in the pan on a wire rack.