Peel and chop the potatoes, carrots, and sweet potatoes into bite-sized pieces.
Dice the onions and mince the garlic. Heat a malm pot over medium heat. Add a bit of oil, then fry the onions and garlic until softened and fragrant. Stir in the tandoori powder and salt, cooking for 1-2 minutes to release the spices' aroma.
Add the chopped vegetables, red lentils, white beans, butter beans, crushed tomatoes, and coconut milk to the pot. Mix well to combine all ingredients.
Cover the pot with a lid and bake in the oven at 390°F (200°C) for at least 1.5 hours. (best at 3 hours)
Check if the vegetables are tender and the stew has thickened. If needed, bake uncovered for an additional 15-20 minutes to reduce excess liquid.