Heat oven to 350 degrees and adjust oven rack to middle position.
Grease a 13x9 inch cake pan.
Grate carrots until you have 3 cups of finely shredded carrots.
Whisk flour, baking powder, baking soda, cinnamon, nutmeg and salt together in large bowl, set aside.
Using stand mixer or mixing bowl with hand mixer beat granulated sugar, brown sugar and eggs on medium-high speed until thoroughly combined, about 45 seconds.
Reduce speed to medium with mixer running, slowly pour in oil (pour along the side of the bowl)
Once oil is poured carefully reduce speed to high and mix until mixture is light in color pour in vanilla and lightly mix.
Stir in by hand the carrots a little at a time. Then add flour mixture a little at a time and stir by hand. Do this until no flour streaks remain and all is fully incorporated.
Scrape batter into prepared pan and lightly tap pan on counter to release air bubbles.
Bake cake until toothpick (which will probably be orange) inserted in the middle comes clean about 35-40 minutes and rotating halfway.
Let cake cool completely on wired racks for two hours.
Run knife along the edges of cake to loosen from pan.
Invert cake onto platter or frost cake as it in pan.
Top with nuts if you wish.
Cream Cheese Frosting
In a large mixing bowl combine cream cheese and butter and vanilla and mix with mixer on medium speed until light and fluffy. Gradually beat in powdered sugar until spreadable consistency.
Top with ½ -1 cup chopped pecans or walnuts, if you wish to.