Preheat oven to 350 degrees F. Lightly grease and flour a 10-inch tube pan. In a medium bowl, stir together the flour, baking powder, baking soda, cinnamon and salt; set aside.

In a large mixing bowl, combine the butter, brown sugar and granulated sugar. Beat with an electric mixer on medium to high speed about 4 minutes until light and fluffy, scraping the bowl occasionally. Add the eggs, one at a time, beating well (about 1 minute) after each addition.

Combine the orange peel, orange juice, the 2 teaspoons of lemon peel, and the 2 tablespoons of lemon juice. Add the juice mixture and the flour mixture alternately to the butter-sugar mixture, beginning and ending with the flour. After each addition, beat at low speed just until smooth.

Using a wooden spoon, stir in the carrots, walnuts, and raisins. Mix well. Note that the carrots should be finely shredded. Unless you have a very fine blade for your food processor, it is best to grate the carrots by hand. The type of grater that is used to grate nutmeg or cinnamon works well.

Pour the batter into the prepared pan, spread evenly. Bake at 350 degrees for 60-65 minutes or until a wooden toothpick inserted near the center comes out clean.

Cool the cake in the pan on a wire rack for 20 minutes. Then loosen the edges with a knife and remove the cake from the pan. Cool completely on the wire rack.

To make the Cream Cheese Frosting - In a medium bowl, combine the softened cream cheese, powdered sugar, the teaspoon of lemon peel, and the 1 tablespoon of lemon juice. Beat with an electric mixer on medium speed until smooth and creamy, scraping the sides of the bowl as needed. When the cake is cool, transfer it to a serving plate and spread with the frosting. Decorate with chopped and whole walnuts if desired.