Bring water to boil. Add carrot, potato, onion and cashews and boil for about 20 minutes over low-medium heat or until soft.
In the meantime, boil pasta by following the directions on its package. Afterward, drain the hot water and rinse macaroni with cold water, then set aside. This step is to prevent pasta from overcooking.
After the boiled vegetables cool down, drain them but save ⅓ of a cup of water for blending.
Add this sauce mixture to a blender along with milk, black salt, nutritional yeast, mustard, turmeric, garlic, black pepper, salt and lemon juice. Blend together into a creamy, smooth texture. Adjust salt and lemon to taste.
Preheat oven to 350 F.
Mix cheese sauce and boiled macaroni well together.
Layer half of mixed mac and cheese on an eight inch baking dish.
Spread choice of vegan cheese over the first layer, then cover with the rest of the mac and cheese.
Top with nutritional yeast and a few sprinkles of optional black pepper and smoked paprika. Bake for 20 minutes.
Remove from oven. Let dish cool down for a few minutes. Serve hot.