Preheat oven to 350 degrees F. Butter and flour 9-inch round baking pan. Place sugar, flour, butter, coffee granules, salt, cinnamon, and nutmeg in a food processor. Pulse on and off until crumbly and completely blended. Do not overprocess. Spoon half crumb mixture into prepared baking pan. Stir baking soda into sour cream and add to remaining crumbs. Add egg and pulse food processor on and off to blend. Pour batter over crumbs in baking pan. Sprinkle nuts over batter. Bake for 40 to 45 minutes.