Preheat oven to 350°F (180°C). Use one 9x13 pan or two, 9 inch cake pans. Prepare pan(s); spray with no-stick cooking spray or grease pans and line bottoms with parchment paper.

In a large bowl, combine flour, baking soda and cinnamon. Then add vanilla, vegetable oil, apple sauce, sugar, and beat until well combined. Blend in carrots and nuts if desired.

Pour batter equally into prepared pan(s) and bake for 50-60 minutes until done when tested. The top should spring back when touched and an inserted toothpick in the center will come out clean.

While the cake is baking make the icing. Using an electric mixer, blend until smooth. Add icing sugar slowly to prevent it spraying out of the bowl.

Remove from oven and let stand for approx. 10 minutes. Then remove from pan and let cool on rack before icing as desired