Cut the cauliflower into bite-sized florets and combine in a bowl with coconut milk, lime juice, and ginger. Toss to coat and marinate for at least 15 minutes.

Preheat oven to 450°F or air fryer to 390°F. Spread cauliflower on a baking sheet or air fryer basket. Sprinkle with arrowroot starch and salt, then roast for 7-10 minutes or air fry for 8-10 minutes until crispy.

In a skillet, melt coconut oil over medium heat. Sauté onion for 3-4 minutes until softened. Add garlic and sauté for an additional 1-2 minutes.

Mix garam masala, curry powder, turmeric, and remaining salt; stir into skillet with onion and garlic. Add marinade and remaining coconut milk, simmer gently.

Add canned diced tomatoes and cook for 5-7 minutes, then blend the sauce until smooth.

Mix the roasted cauliflower into the sauce, cook briefly, and serve hot, garnished with cilantro.