• Preheat oven to 350°F. Grease a 9×13-inch baking dish.

  In a small bowl, combine the brown sugar, cinnamon, and nuts (if using). Set aside.

  In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.

  In a large bowl, cream the butter and granulated sugar until light and fluffy.

  Add eggs one at a time, mixing well after each addition. Stir in vanilla.

  Mix in the sour cream until smooth.

  Gradually add the dry ingredients, mixing just until combined.

  Spread half of the batter into the prepared pan. Sprinkle with half of the cinnamon topping.

  Spread the remaining batter over the topping and finish with the remaining cinnamon mixture.

  Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean.

  Cool slightly before serving.

Notes

• Do not overmix the batter—this keeps the cake tender.

  Nuts are optional and can be omitted without affecting the bake.

  Store covered at room temperature for up to 2 days or refrigerate longer.