Fat-Free Mocha Fudge Cake
["2 c. unbleached flour", "1 1/4 c. sugar", "1/2 c. cocoa powder", "1 tsp. baking powder", "1/2 tsp. baking soda", "1/4 tsp. salt", "3/4 c. prune butter", "1 1/2 c. plus 2 Tbsp. coffee, at room temperature", "2 tsp. vanilla", "1/2 c. chopped walnuts", "3 to 4 Tbsp. confectioners sugar"]
["Combine flour, sugar, cocoa, baking powder, baking soda and salt.", "Mix well.", "In separate bowl, combine prune butter, coffee and vanilla.", "Mix well.", "Add mixture to flour mixture.", "Mix well. Add walnuts.", "Put in a 9 x 13-inch pan coated with nonstick cooking spray; spread evenly.", "Bake at 350\u00b0 for 30 to 35 minutes. Sift confectioners sugar over cool cake."]
["flour", "sugar", "cocoa powder", "baking powder", "baking soda", "salt", "butter", "coffee", "vanilla", "walnuts", "confectioners sugar"]