Preheat the oven to 350 degrees F. Line cupcake tins with 12 cupcake liners.
In a mixing bowl, sift together the salt, all purpose flour, baking soda, baking powder, grated nutmeg, and ground cinnamon. Whisk well and set aside.
In a large measuring cup, whisk together the whole milk, vanilla extract, and sour cream. Set aside.
With an electric mixer, mix together the softened unsalted butter, light brown sugar, and granulated sugar. Allow to mix for 3-5 minutes. Then add the 2 egg whites to the electric mixer.
Reduce the speed of the electric mixer to low. Alternate between adding 2/3 cup of dry ingredients and 2/3 cup of wet ingredients to the electric mixer. Continue this process until all ingredients are added. Turn off the mixer as soon as all the flour is fully incorporated.
Spoon the batter into the cupcake liners. Fill until two-thirds full (3-4 tablespoons of batter per cupcake liner). For the cinnamon sugar: In a small bowl, sift together the ground cinnamon and granulated sugar. Sprinkle roughly 1/2 teaspoon on top of each cupcake before baking.
Bake for 16-18 minutes or until inserted toothpick comes out clean. Leave in muffin tin for 2 minutes before moving to a cooling rack. Cool completely before frosting.