In large skillet, heat oil over medium heat. Add onion, garlic, potatoes and ginger and cook, stirring often, until fragrant, about 2 minutes.Add curry powder and cumin and cook 1 minute, stirring.Add tomatoes and chickpeas; bring to a boil, stirring. Add water slowly and spinach.Place cauliflower on top of stew. Cover and simmer until cauliflower is tender,. 10 minutes. Season with salt and cayenne.