Preheat oven to 350 degrees. Coat inside of three 9-inch round layer-cake pans with non-stick cooking spray. Line the bottoms with wax paper and set aside.
Spread walnuts in a pie plate and bake for 8 to 10 minutes at 350 degrees, or until fragrant. Let cool; chop coarsely.
Toasting the walnuts brings out their nutty flavor, and means you don't need to use as many as in traditional recipes.
In a medium-sized bowl, stir together flour, cinnamon, baking powder, baking soda and salt. In a large bowl, whisk together eggs and egg whites. Add sugar, prune puree and oil and whisk until smooth. Add the flour mixture to the egg mixture and stir with a wooden spoon until blended. Stir in carrots, pineapple and the toasted walnuts. Divide the batter among the prepared pans and bake for 30 to 35 minutes at 350 degrees, or until a cake tester inserted in the center comes out clean.
Let cool for 5 minutes in the pan on a rack. Loosen edges and invert cakes onto racks. Peel off paper and let cool completely.
TO MAKE PRUNE PUREE: In a food processor, combine 6 ounces (1 cup) pitted prunes with 6 tablespoons hot water; process until smooth. Makes 1 cup. One cup of prune puree contains 407 calories and 1 gram of fat; a cup of butter contains 1,600 calories and 182 grams of fat; and a cup of oil contains 1,944 calories and 218 grams of fat.
FROSTING In a mixing bowl, combine cream cheese, sugar and vanilla; beat with an electric mixer until smooth and creamy.
TO ASSEMBLE CAKE: Place 1 cake layer on a serving plate. Spread a scant 1/2 cup of frosting over it. Top with another cake layer and spread another scant 1/2 cup frosting. Place third layer on top and spread with remaining frosting. Serves 16.
Calories: 310 per serving; Protein: 6 grams; Fat: 10 grams; Carbohydrate: 52 grams; Sodium: 392 milligrams; Cholesterol: 34 milligrams.