Add onion, peppers, potatoes, carrots, garlic and water to a sauce pan and bring to a boil. Cover the pan and simmer for 15 minutes, or until vegetables are very soft.
While the vegetables are simmering, cook pasta until al dente. Drain pasta (do not rinse) and set aside with the lid on to keep pasta warm.
Place the almond milk, cashews, salt, coconut oil, mustard, lemon juice and black pepper in a blender cup. Drain water from softened vegetables and add to blender; process until perfectly smooth (use Soup button if you have a Blendtec).
In a large bowl, toss the cooked pasta and blended cheese sauce until completely coated. Serve immediately.