In a medium bowl, combine the chopped nuts, brown sugar, corn syrup, and cinnamon. Mix well until evenly distributed. Set aside.
In a large mixing bowl, combine the vanilla cake mix, melted butter, eggs, milk, and sour cream. Using a whisk, mix until smooth and well combined.
Preheat your oven to 350°F (175°C). Grease your baking pan with a bit of butter. Pour half of the cake batter into the prepared pan, spreading it evenly. Sprinkle the nut mixture over the batter, then pour the remaining batter on top, smoothing it out to cover the nuts completely.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean. While the cake is baking, prepare the syrup.
In a small saucepan, combine honey, water, lemon juice, and 2 tablespoons of butter. Bring to a gentle boil, then reduce the heat and let it simmer for about 10 minutes, stirring occasionally.
Once the cake is done baking, remove it from the oven and immediately pour the warm syrup over the hot cake, ensuring it soaks in well. Allow the cake to cool in the pan on a wire rack.
Once cooled, cut into squares and serve. Enjoy warm or at room temperature, paired with tea or coffee if desired.