Melt butter in a large saucepan over medium heat. Add onion; sauté 3 minutes. Stir in garlic and ginger; sauté 1 minute. Add salt and next 5 ingredients; cook 1 minute. Add water, scraping pan to loosen browned bits. Stir in tomato, potato, and lentils. Bring to a boil; cover, reduce heat, and simmer 20 minutes or until potato mixture is tender.
Stir parsley and vinegar into potato mixture. Serve over Lemon-Cilantro Rice.