For CAKE, preheat oven to 350°. Line bottoms of three 9-inch round cake pans** with parchment or waxed paper, then grease and flour bottoms and sides of pans; set aside.
Combine flour, baking powder, cinnamon, baking soda, ginger and salt in medium bowl; set aside.
Beat I Can't Believe It's Not Butter!® Spread with sugar in large bowl with electric mixer until light and creamy, about 5 minutes. Add orange juice, then eggs, one at a time, beating 1 minute after each addition. Beat in flour mixture, then carrots and chopped walnuts. Evenly spread into prepared pans.
Bake 25 minutes or until toothpick inserted in center of cakes comes out clean. Cool 10 minutes on wire rack; remove from pans and cool completely.
For FROSTING, beat cream cheese, Spread and confectioners sugar in medium bowl with electric mixer until light and creamy, about 5 minutes. Spread top of one cake layer with 1/3 of the frosting. Top with second cake layer and another 1/3 of the frosting. Top with remaining cake layer and remaining frosting, leaving 1-inch border around edge of top layer. Garnish with walnut halves.
*Carrots can be grated in a food processor or blender until size of finely chopped nuts.
**For TWO-LAYER CARROT CAKE, bake in two 9-inch round cake pans prepared as above. Bake 33 minutes or until toothpick inserted in center of cakes comes out clean. Evenly spread frosting on cool cake layers.