The recipe for this moist, dense, and not-too-sweet cake -- a slice is perfect for an afternoon snack -- comes from Jean Josephson of Portland, Oregon.
Preheat oven to 325 degrees. Butter and flour a nonstick Bundt pan (12-cup capacity), tapping out excess flour; set aside.
Bring a small saucepan of water to a boil; remove from heat, and add prunes. Cover, and let soak 10 minutes. Drain prunes and finely chop; set aside.
Meanwhile, in a large bowl, whisk together flour, granulated sugar, cinnamon, cloves, nutmeg, salt, and baking soda; set aside. In a medium bowl, whisk together oil, buttermilk, and eggs. Add oil mixture to flour mixture; mix just until combined. Stir in prunes and nuts.
Spoon batter into prepared pan, and bake until a toothpick inserted in center of cake comes out clean and the cake has pulled away completely from sides of the pan, 1 hour and 45 minutes to 2 hours.
Immediately invert onto a cooling rack; let cool completely. Dust with confectioners' sugar, if desired.
Even if it looks done, be sure to bake this cake for as long as the recipe specifies so it can caramelize and easily release from the pan.