Preheat oven to 350°F (175°C).

In a large bowl, combine yellow cake mix, eggs, sour cream, oil, and vanilla instant pudding.

Mix well until all ingredients are fully incorporated.

In a separate bowl, combine brown sugar, cinnamon, and nuts.

Pour half of the cake batter into a greased baking pan.

Sprinkle half of the brown sugar mixture over the batter.

Pour the remaining cake batter over the brown sugar mixture.

Sprinkle the remaining brown sugar mixture over the top.

Bake for 35 minutes, or until a toothpick inserted into the center comes out clean.

Let cool slightly before serving.