Heat oil in large pan over medium-high heat. Add onion and ginger, cover, and cook for 3 minutes. Add curry powder and garlic, and cook 30 seconds, stirring often. Add cauliflower and potatoes, and cook for 5 minutes, stirring often, until they start to soften. Add tomatoes, 1/4 c cilantro, 1/2 c water, and salt. Simmer, reduce heat, and cook, covered for 15 minutes, until vegetables are tender. Stir in remaining cilantro and cook, covered, for 2 more minutes. Serve alone or over rice.