In a large skillet, saute the mushrooms over medium-high heat for about 5 minutes.
Add in the spinach and sun-dried tomatoes and cook another 5 minutes or until the spinach is tender. Add a tablespoon or 2 of water if needed to prevent sticking. Turn the heat to low.
While you are cooking the veggies, begin cooking the pasta according to package directions. When finished, drain, and set aside.
While pasta is cooking, make the sauce. Add the cashews, nutritional yeast flakes, lemon juice, garlic, water, and salt to a high-speed blender, and blend until smooth and creamy.
Add the pasta and sauce to the cooked veggies and warm through. Serve!