Preheat the oven to 350°.

In a large bowl, combine vanilla cake mix, eggs, vegetable oil, buttermilk, and vanilla. Mix until you have a thick cake batter and everything is combined. Set aside.

In a small bowl, combine brown sugar, flour, cinnamon, and melted butter. Stir until all ingredients are combined.

Prepare the Bundt pan by spraying it liberally with nonstick cooking spray.

Pour half of the cake batter into the prepared pan. Spoon over half of the cinnamon swirl mixture and use a toothpick or skewer to swirl the cinnamon mixture throughout the batter.

Pour the remaining cake batter into the pan, top with the remaining cinnamon swirl mixture, and repeat swirling it into the cake batter.

Bake for 40-45 minutes or until a toothpick inserted in the center comes out with only a few crumbs. Remove from the oven and allow the cake to cool in the pan for at least 15 minutes.

Invert the cake onto your serving plate and allow it to cool completely.

In a bowl, combine softened cream cheese and butter, mixing until smooth. Add vanilla extract and powdered sugar, and continue to mix until you have a frosting consistency. If too thick, add a tablespoon of milk or microwave for 20 seconds.

Add the cream cheese glaze to a piping bag, cut a triangle from the bottom, and using a zigzag motion, cover the top of the cake with the cream cheese glaze.

In a small bowl, combine cinnamon and sugar, and mix until evenly distributed. Sprinkle as much of the mixture over the top of the cake as desired.