Preheat your oven to 350°F (175°C) and prepare a 9x13-inch baking pan with non-stick spray.

In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, ground ginger, ground nutmeg, and salt.

In another bowl, combine vegetable oil, eggs, brown sugar, granulated sugar, crushed pineapple, and vanilla extract; blend until smooth.

Stir in grated carrots and walnuts (if using) into the wet mixture.

Gradually add dry mixture to the wet ingredients, stirring gently until just combined.

Pour the batter into the prepared baking pan and smooth the top.

Bake for 35-45 minutes, or until a toothpick inserted comes out clean.

Allow to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

For frosting, beat cream cheese and softened butter until smooth, then mix in powdered sugar and vanilla until spreadable.

Once cooled, frost the cake with the cream cheese frosting.