Preheat your oven to 350°F (175°C) and grease a 9×9 inch baking pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, then stir in the vanilla.
In a separate bowl, combine the flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the creamed mixture, alternating with the sour cream.
In a small bowl, mix the brown sugar, cinnamon, and nuts for the topping.
Spread half of the batter into the prepared pan. Sprinkle half of the topping over the batter. Repeat with the remaining batter and topping.
Bake in the preheated oven for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.
Allow the coffee cake to cool before serving. Enjoy!