Prepare the cream-sauce. At a high-speed blender, mix 1 cup of batter, the soaked cashews and tomato paste, till creamy and smooth. Put aside.
Warm olive-oil in a skillet or large saucepan pan over medium-heat. Then sauté the diced onion till starting to soften, then add the garlic and continue to sauté another minute till fragrant.
Add 3 cups of broth, the penne, nutritional-yeast, roasted red-peppers, oregano, red-pepper flakes and sea-salt and stir till ingredients are evenly dispersed.
Cover and bring to a strong simmer, then turn down heat to medium-low. Continue to simmer covered, stirring occasionally, for 15 minutes. You want the pasta to be mostly cooked before adding the cream-sauce.
When the pasta has nearly cooked to your preferred feel, uncover and put in the cream-sauce. Stir till the noodles are evenly coated, then stir in the spinach.
Cover for a couple of minutes to allow the spinach wilt, warm the cream-sauce and finish cooking the noodles.