Sift together flour, salt, soda, and cinnamon. Set aside. In the stand mixer bowl, mix the sugar, oil, and eggs for 2 minutes, scraping sides of bowl often.
Gradually add the flour mixture and beat at low speed for 1 minute. Stir in carrots and nuts until well mixed. Pour batter into prepared pans and bake for 55-65 minutes.
Remove from oven and allow cake to cool in pans for 10 minutes. Remove from pans and cool completely on wire racks. When cake has cooled, spread cream cheese frosting between layers, along sides, and on top. Sprinkle chopped walnuts on top or press them into the sides of the cake. Store cake in the refrigerator.