Preheat your oven to 350 degrees F. and line a muffin tin with cupcake liners.
In a large bowl, combine the flour, cinnamon, salt, baking powder, and baking soda. Set it aside.
Add the brown sugar, granulated sugar, eggs, carrots, oil, vanilla extract, and sour cream to a large bowl and mix well.
Add the flour mixture to the egg mixture and mix until well combined but don't overmix.
Divide the batter evenly into your prepared muffin tin and bake for 22 minutes or until a toothpick inserted in the center comes out clean or with fine crumbs. The cupcakes won't rise much.
Allow the cupcakes to cool completely before frosting. Garnish with chopped walnuts, if desired, and enjoy!