1. Preheat oven to 350°. Place walnuts in a single layer on a baking sheet, and bake 6 to 8 minutes or until lightly toasted. Transfer to a plate to cool; chop.
2. Place cranberries in food processor and process until coarsely chopped. Set aside.
3. Beat butter at medium speed with an electric mixer until fluffy; gradually add brown sugar, beating well. Add eggs, 1 at a time, beating until blended after each addition.
4. Combine flour and next 6 ingredients; add to butter mixture alternately with buttermilk, beginning and ending with flour mixture, beating at low speed until blended after each addition. Stir in vanilla extract, pumpkin and reserved walnuts and cranberries. Spoon batter into a greased 12-cup Bundt pan, smoothing top.
5. Bake 50 to 55 minutes or until a wooden toothpick inserted in center comes out clean. Cool cake in pan on a wire rack 10 minutes; remove from pan, and cool completely on rack.
6. Stir together powdered sugar and 1/4 cup maple syrup in a small bowl until smooth. Stir in remaining maple syrup, 1 teaspoon at a time, until glaze is pourable but not too thin. Drizzle glaze over cooled cake.