Preheat your oven to 350°F (175°C).

Grease a 9x13 inch baking pan with butter or cooking spray.

In a large bowl, whisk together the flour, baking powder, baking soda, salt, and ground cinnamon.

In another bowl, cream the softened butter and granulated sugar until light and fluffy.

Beat in the eggs one at a time, followed by the vanilla extract.

Gradually add the dry mixture to the wet ingredients, alternating with the sour cream.

In a small bowl, mix the brown sugar and chopped nuts with a bit of cinnamon.

Pour half of the batter into the prepared pan, sprinkle half of the topping, then add the remaining batter and top with the rest of the cinnamon mixture.

Bake for about 30 minutes, or until a toothpick comes out clean.

Let the cake cool in the pan for 10 minutes before transferring it to a wire rack.