Heat oven to 350°F
Spray a 9x13 baking dish with cooking spray and set aside.
In bowl of an electric mixer combine cake mix, oil, eggs and sour cream with and mix until combined. Pour about half of the mixture into the prepared baking dish. Set aside.
1 box yellow cake mix, ⅔ cup vegetable oil, 4 eggs, 8 oz sour cream
In small mixing bowl, stir together brown sugar, cinnamon, and pecans until combined. Sprinkle butter and nut mixture on top of the batter that is in the dish, covering the batter.
1 cup packed brown sugar, 2 teaspoons ground cinnamon, ⅓ cup chopped pecans
Pour remaining half of the batter on top of the brown sugar cinnamon mixture. Spread to cover the top.
Bake 40-45 minutes or until golden brown.
While cake is baking, make the frosting.
In the bowl of an electric mixer combine confectioner’s sugar, milk, and vanilla until smooth.
1 cup confectioner's sugar, 1 tablespoon milk, 1 teaspoon vanilla extract
Once cake is out of the oven, make holes in the cake with the tines of a fork or the back of a wooden spoon. Spread frosting over warm cake and let set.