Sweet-Potato Layer Cake with Orange-Cream Cheese Frosting

Preparation

1. For cake:

   Step 1

   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.

   Step 2

   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.

2. For frosting:

   Step 3

   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.

   Step 4

   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.)