Place beef brisket, fat side down, in deep roasting pan. Sprinkle brisket with onion, salt, pepper and garlic powder. Pour chili sauce over brisket. Cover tightly and cook in slow oven (325 degrees F.) for 3 hours. Pour beer over brisket. Increase oven temperature to moderate (350 degrees F.) and continue cooking, covered, 30 minutes. Place brisket on large serving platter and surround with Wild Rice Amadine. Garnish with sliced tomatoes and parsley. Slice brisket very thin and serve with hot cooking liquid.