In a covered medium saucepan cook sweet potatoes in enough boiling water to cover for 10 to 12 minutes or until tender.
Meanwhile, in a large nonstick skillet heat oil over medium-high heat. Add onion; cook for 5 minutes. Add sweet pepper; cook for 3 minutes more. Add tomatoes, brown sugar (if using), salt, and black pepper. Bring to boiling; reduce heat. Simmer, uncovered, about 5 minutes or until most of the liquid evaporates.
Drain the cooked sweet potatoes well. Stir sweet potatoes into tomato mixture. Garnish with parsley leaves.