Pulse ginger and garlic in food processor until finely chopped. Add tomatoes with juice and cayenne pepper, and pulse until combined. Set aside.Heat oil in saucepan over medium heat. Add onion and bell pepper, and sauté 10 minutes, or until softened. Stir in potatoes, carrots, garam masala, and chili powder. Cover, reduce heat to medium-low, and cook 10 minutes, stirring occasionally.Add cauliflower, tomato mixture, and 1/2 cup water. Simmer 20 minutes. Remove from heat, and stir in coconut milk. Season with pepper.