Add onion to stock pot; cook and stir 5 minutes or until tender. Add 1/2 cup water. Return brisket; bring to a boil. Reduce heat; cover tightly and simmer 2-1/4 hours. Add carrots, brown sugar, lemon juice, salt, cinnamon and pepper; continue cooking, covered, 30 to 45 minutes or until brisket is fork-tender. Remove brisket and carrots; keep warm.