Combine beef consommé and soy sauce. Halve and juice lemons. Add juice to consommé and soy sauce. Chop garlic cloves and add to mixture. Add liquid smoke, if desired. Place brisket in oven proof pan, fat side up. Pour mixture over brisket and cover tightly. Marinate in refrigerator for 24 to 48 hours.
Cook brisket in 300 degree oven for about 40 minutes per pound.
