In a sauce pan, heat coconut milk and add the lemongrass. After a boil, take the pan off the heat, cover and keep it aside for about 30-40 minutes. Meanwhile roast the veggies for sauce.
Cut the tomatoes in half. Lay them on a lined sheet pan, cut side up. Drizzle olive oil. Sprinkle salt pepper and jaggery or sugar. Place the sheet pan in the oven along with garlic, and roast them for 30-45 minutes until very soft and caramelized.
Lower the heat to medium low heat. Add salt, pepper and the pumpkin coconut puree.
Garnish with fresh herbs and serve hot.
You could use the store bought arrabbiata sauce and blend it with the pumpkin puree and coconut milk, if you are short of time.