Leftovers are great for breakfast.
Preheat oven to 350°F. Butter and flour 8-inch square metal baking pan. Mix first 4 ingredients in medium bowl to blend. Whisk sugar, butter and egg in large bowl until smooth. Whisk in dry ingredients alternately with buttermilk, beginning with dry ingredients. Fold in nuts. Transfer batter to prepared pan. Bake until tester inserted in center comes out clean, about 1 hour. Cool slightly in pan on rack. Serve warm with ice cream.