Preheat your oven to 350°F (175°C). Lightly grease a 9×13 inch baking pan to prevent sticking.
In a large mixing bowl, combine the cake mix, brown sugar, sour cream, cinnamon, pecans, vegetable oil, eggs, and water. Beat with an electric mixer or whisk until all ingredients are well blended and smooth.
Pour the batter into the prepared baking pan, spreading evenly. Bake in the preheated oven for about 40 minutes, or until a toothpick inserted in the center comes out clean.
Remove the cake from the oven and let it cool completely on a wire rack. Once cooled, spread the Duncan Hines® Creamy Vanilla Frosting evenly over the top. Slice and serve.