In a large skillet heat oil over medium. Add onion and cook, stirring, until softened, 6-8 minutes. Add garlic, peppers, ginger, garam masala or curry powder, turmeric, and salt and cook, stirring, 1 minute more. Stir in tomatoes, cauliflower, and 1 cup water. Bring to a simmer, cover, and cook until cauliflower is very soft, about 10 minutes. Transfer to a blender and puree.