Preheat oven to 350 F. Line two muffin tins with paper liners and set aside.
Combine flour, baking soda, baking powder, salt, cinnamon and nutmeg in a medium bowl and set aside.
Peel the carrots, and finely grate them (I use my food processor for this - you can also use a box grater). Place the grated carrots in a large bowl.
Add the eggs, buttermilk, vanilla, sugar, oil and orange zest to the bowl with the carrots and whisk until thoroughly combined.
Gently stir the flour mixture into the carrot mixture until just combined. Be careful not to overmix.
Scoop batter evenly into prepared liners, filling each ⅔ - ¾ full. Bake for 20-22 minutes, until a toothpick inserted in the center comes out clean. Cool for five minutes in pans, then remove to racks to cool completely.
In a large bowl or the bowl of a stand mixer, beat cream cheese on medium speed until fluffy, about two minutes. Add the butter and beat until well-incorporated and fluffy, another two minutes. Beat in the brown sugar, vanilla, and cinnamon. Add the powdered sugar a few tablespoons at a time until desired consistency is reached (I usually use about 3 cups). Beat for an additional two minutes. Pipe or spread onto cupcakes (if spreading rather than piping, you can halve the frosting recipe).
Top with garnishes of choice - toasted walnuts, grated carrots, etc.
Recipe by Baked In at https://www.baked-in.com/2013/04/19/carrot-cake-cupcakes/