Preheat your oven to 350
Empty the box cake mix into a bowl.
Add brown sugar and cinnamon and mix well
Add grated carrots and chopped walnuts and mix till everything is evenly coated.
Add water, oil and slightly beaten eggs. Mix till well combined. About 2 mins. You don't have to worry about over-mixing.
Butter a 9x13 baking dish or you can use two 9 inch round cake pans if you want to do a double layer cake. If you're using round cake pans make sure to line them with parchment paper so your cakes will release from the pans.
Put the batter in your pans and bake following the directions on the back of the box.
Bake for 34 to 38 mins for a 9x13 pan and 29 to 33 min for two 9 inch pan.
Frost with your favorite frosting. I love cream cheese frosting.