Sweet potatoes make this moist; cranberries and walnuts add texture and color.  
Cake
2 pounds tan-skinned sweet potatoes (about 3 medium)
3 cups cake flour
2 teaspoons baking soda
2 teaspoons baking  powder
2 teaspoons ground cinnamon
1 teaspoon ground ginger
1/2  teaspoon salt
1/4 teaspoon ground cloves
1 cup vegetable oil
1  cup sugar
1 cup (packed) golden brown sugar
4 large eggs
2/3 cup  plus 1/4 cup chopped walnuts, toasted
2/3 cup plus 1/4 cup dried  cranberries 
Frosting
1 8-ounce package cream cheese, room  temperature
1/2 cup (1 stick) unsalted butter, room temperature
31/4  cups powdered sugar, sifted
2 tablespoons frozen orange juice concentrate,  thawed
1/2 teaspoon vanilla extract
1/4 cup sliced candied orange  peel
3 tablespoons sugar 
Preparation
For cake:
Preheat oven  to 400°F. Pierce potatoes with fork; place on small baking sheet. Roast potatoes  until soft, about 1 hour. Cool, peel, and mash potatoes. Measure 2 cups mashed  potatoes; cool to lukewarm (reserve any remaining potatoes for another use).  Reduce oven temperature to 350°F. 
Butter and flour two 9-inch-diameter  cake pans with 2-inch-high sides; line pans with parchment. Sift flour and next  6 ingredients into medium bowl. Combine oil, 1 cup sugar, and brown sugar in  large bowl; whisk until smooth. Whisk in eggs 1 at a time, then mashed sweet  potatoes. Whisk in flour mixture in 3 additions. Stir in 2/3 cup walnuts and 2/3  cup cranberries. Divide batter between prepared pans. Bake cakes until tester  inserted into center comes out clean, about 30 minutes. Cool cakes completely in  pans on racks. 
For frosting:
Using electric mixer, beat cream cheese  and butter in large bowl until fluffy. Beat in powdered sugar, scraping down  bowl often. Beat in orange juice concentrate and vanilla. 
Cut around pan  sides; turn out cakes. Peel off parchment. Place 1 cake layer, flat side up, on  platter. Spread 3/4 cup frosting over. Top with second cake layer, flat side  down. Spread remaining frosting over top and sides of cake. Combine orange peel,  3 tablespoons sugar, remaining 1/4 cup walnuts, and 1/4 cup cranberries in small  bowl. Stir to coat with sugar. Transfer to sieve; sift off excess sugar.  Sprinkle fruit and nut mixture decoratively atop cake. Chill until frosting  sets, at least 2 hours. (Can be made 1 day ahead. Cover with cake dome; keep  chilled. Let stand at room temperature 1 hour before serving.)