The tangy flavor of buttermilk in the cake complements its creamy citrus frosting.
Bring carrot and 1 cup water to a boil in a medium saucepan. Cover, reduce heat, and simmer 15 minutes or until tender. Do not drain.
Process carrot mixture in a blender or food processor until smooth, stopping to scrape down sides. Measure 1 cup puree, and set aside.
Beat butter and sugars at medium speed with an electric mixer until blended. Add eggs, 1 at a time, beating just until blended after each addition.
Combine cake flour and next 4 ingredients. Combine carrot puree, buttermilk, and vanilla. Gradually add flour mixture to butter mixture alternately with carrot mixture, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in pecans. Spoon batter into a greased and floured 13- x 9-inch pan.
Bake at 350° for 45 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack. Spread with Citrus Cream Cheese Frosting.
NOTE: Batter may be spooned evenly into 3 greased and floured 9-inch round cake pans. Bake at 350' for 30 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes; remove from pans, and cool on wire racks. Spread Citrus Cream Cheese Frosting between layers and on top and sides of cake.