Bring a large pot of water to boil. Use enough water so all of the cauliflower can be immersed in it.
Add salt, turmeric and chili and blanch/cook the whole cauliflower.
Cover and cook for 4 minutes on each side
In a pan, add oil and heat over medium heat. Add chopped onion and saute until golden,
Add ginger, garlic chili and saute for another 2 minutes.Add the spices and mix.
Add tomatoes, salt, sugar, fenugreek leaves, mix and cook covered until tender. Mash the larger pieces.
Cool slightly, then blend with coconut milk and cashews into a smooth thick puree.Taste and adjust salt, spice.
Preheat the oven to 400 degrees F / 200ºc. Oil the baking dish if desired. Place the blanched cauliflower in a baking dish. Slowly drop the puree on top to cover the entire head of the cauliflower.
Keep about a 1/3 of the sauce to serve on the side later.
Bake in pre-heated 400 degrees F / 200ºc for 40-45 minutes till the cauliflower is dry to touch and sauce thickens a bit. Turn the dish around after 30 minutes.
Heat the remaining sauce to just about a boil so it thickens and serve on the side.