Preheat the oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a large mixing bowl, combine flour, baking powder, baking soda, cinnamon, and salt.
In another bowl, whisk together sugar, oil, and eggs until smooth.
Gradually add dry ingredients to wet mixture, mixing just until combined.
Fold in grated carrots and crushed nuts.
Divide the batter among the cupcake liners, filling each about 2/3 full.
Bake for 20-25 minutes, or until a toothpick inserted comes out clean.
Allow to cool for 5 minutes before transferring to a wire rack.
Prepare cream cheese frosting by beating cream cheese, butter, and sugar until smooth.
Frost cooled cupcakes and top with additional nuts if desired.