Line (3) 9 inch cake pans with parchment paper and spray with nonstick baking spray.
In a large bowl combine sugar, oil, and eggs. Stir in baking soda, baking powder, salt, and cinnamon.
Add flour a little at a time until just combined. Do not overmix.
Fold in shredded carrots and pecans.
Evenly divide batter between 3 prepared pans. Bake for 25-30 minutes. Cool completely.
For the Frosting
In a large bowl beat butter, cream cheese, and vanilla until light and fluffy.
Gradually add powdered sugar until you reach your desired consistency.
Assembly
Cut off the domes of the cake layers.
Spread pecans on a baking sheet. Toast at 350 degrees for 5-10 minutes stirring once or twice.
Place the first layer of the cake onto a 10 inch cake board. Add around 1 cup of frosting to first layer and smooth. Repeat with remaining layers.
Place the last cake layer on top. Add a thin coat of frosting on the top and down the sides. Refrigerate for 15-20 minutes and then add a second layer of icing.
Coat sides and top of cake with pecans if desired. Enjoy!