Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.

In a medium bowl, whisk together flour, baking soda, baking powder, salt, cinnamon, and nutmeg. Set aside.

In a large bowl, whisk together granulated sugar, brown sugar, and vegetable oil until well combined. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.

Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Fold in grated carrots, crushed pineapple, and walnuts (if using).

Divide the batter evenly among the prepared cupcake liners, filling each about two-thirds full.

Bake for 16–18 minutes, or until a toothpick inserted into the center comes out clean. Allow cupcakes to cool completely on a wire rack before frosting.

In a large bowl, beat cream cheese and butter together until smooth and creamy.

Gradually add powdered sugar and vanilla extract, beating until light and fluffy.

Frost cooled cupcakes using a piping bag or spatula. Optionally, garnish with chopped walnuts or a sprinkle of cinnamon.