Preheat oven to 350ºF. For topping: Combine topping ingredients; set aside.
For cake: Lightly spray 8 x 8-inch baking pan with vegetable oil baking spray; set aside.
In medium bowl, combine flour, baking soda, baking powder and salt; set aside.
In large bowl, cream butter and sugar using electric mixer. Add eggs and vanilla extract; mix well. Alternately add flour mixture and sour cream to butter mixture, mixing until just combined.
Spread half of cake mixture in pan. Sprinkle half of topping over cake mixture; repeat with remaining cake mixture and topping. Bake 45 to 50 minutes or until toothpick inserted in center is clean when removed. Remove from oven; cool completely before serving.
